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PubMed1993

NTP Toxicology and Carcinogenesis Studies of Pentachloroanisole (CAS No. 1825-21-4) in F344 Rats and B6C3F1 Mice (Feed Studies).

Pentachloroanisole is a chlorinated aromatic compound which is widely distributed at low levels in the environment and in food products. Formation of pentachloroanisole in the environment may result from the degradation of structurally related, commercially important, ubiquitous chlorinated aromatic compounds such as pentachlorophenol and pentachloronitrobenzene which are known rodent toxins or carcinogens. Toxicology and carcinogenesis studies were conducted by administering pentachloroanisole (>99% pure) in corn oil by gavage to groups of male and female F344/N rats and B6C3F1 mice for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium strains, mouse lymphoma cells, and Chinese hamster ovary cells. 16-DAY STUDIES IN RATS: Groups of five male and five female F344/N rats were administered pentachloroanisole in corn oil by gavage once per day, 5 days per week, for 16 days at doses of 0, 100, 125, 150, 175, or 200 mg/kg body weight. Deaths occurred during days 2 and 3 in rats receiving doses of 125 mg/kg or greater; these deaths were considered directly related to pentachloroanisole administration. No biologically significant changes in mean body weight gains or final body weights were noted in the 100 mg/kg groups of rats. Because of the high early mortality rate, valid comparisons of body weight differences in other dose groups could not be made. Inactivity was noted in all dose groups. Rats administered doses of 125 mg/kg or greater also exhibited dyspnea. 16-DAY STUDIES IN MICE: Groups of five male and five female B6C3F1 mice were administered pentachloroanisole in corn oil by gavage once per day, 5 days per week, for 16 days at doses of 0, 100, 175, 250, 325, or 400 mg/kg. Deaths occurred during days 2 and 3 in mice receiving doses of 175 mg/kg or greater; these deaths were considered directly related to chemical administration. No biologically significant changes in mean body weight gains or final body weights were noted in 100 mg/kg males or 100 or 175 mg/kg females. Because of the high early mortality rate, valid comparisons of body weight differences in other dose groups could not be made. Inactivity was noted in dosed mice. 13-WEEK STUDIES IN RATS: Groups of 10 male and 10 female rats were administered pentachloroanisole in corn oil by gavage once per day, 5 days per week, for 13 weeks at doses of 0, 40, 80, 120, 140, or 180 mg/kg body weight. Most rats receiving doses of 120 mg/kg or greater died during the first week of the study as a direct result of pentachloroanisole administration. Mean body weight gains of males administered 40 or 80 mg/kg and of females administered 40, 80, or 120 mg/kg pentachloroanisole were significantly lower than those of the controls. Most dosed rats exhibited temporary inactivity for several hours after dosing. Relative liver and kidney weights of males administered 40 or 80 mg/kg and absolute and/or relative liver and kidney weights of females administered 40 to 120 mg/kg were significantly greater than those of the controls. Lesions observed in males administered 80 mg/kg or more and in females administered 120 mg/kg or more included pulmonary congestion, hemorrhage, and/or edema, meningeal congestion, and hepatocellular necrosis, glycogen depletion, and degeneration of biliary epithelium in the liver. 13-WEEK STUDIES IN MICE: Groups of 10 male and 10 female mice were administered pentachloroanisole in corn oil by gavage once per day, 5 days per week, for 13 weeks at doses of 0, 40, 80, 120, 140, or 180 mg/kg body weight. Most mice administered doses of 120 mg/kg or higher died during the first week of the study as a direct result of pentachloroanisole administration. Mean body weight gains of females administered 40 to 140 mg/kg were significantly greater than that of the controls, but those of dosed males were similar to that of the controls. Most dosed mice exhibited temporary inactivity for several hours after dosing. Absolute and relative liver weights of males administered 80 mg/kg, absolute and relative liver weights of femats of females administered 40 to 180 mg/kg, and absolute and relative kidney weights of females administered 80 to 180 mg/kg pentachloroanisole were also significantly greater than those of the controls. Lesions observed in males administered 40 mg/kg or more and in females administered 80 mg/kg or more included pulmonary congestion and/or edema, adrenal congestion, lymphoid depletion of lymph nodes and thymus, hepatocellular cytomegaly and karyomegaly, and pigment accumulation in hepatocytes and Kupffer cells. 2-YEAR STUDIES IN RATS: Based on the chemical-related mortality and liver lesions seen in the 16-day and 13-week studies, doses selected for the 2-year studies were 0, 10, 20, and 40 mg/kg for males and 0, 20, and 40 mg/kg for females. Groups of 70 male and 70 female rats were administered pentachloroanisole in corn oil by gavage 5 days per week for up to 2 years. At 9 and 15 months, up to 10 animals per group were selected for interim evaluations. Survival, Body Weights, and Clinical Findings: The survival of high-dose males was significantly decreased (vehicle control, 24/50; low-dose, 20/50; mid-dose, 24/50; high-dose, 14/50); most deaths in the high-dose group occurred at or before week 16. The majority of deaths in the mid- and high-dose groups may have been due to pentachloroanisole-related hyperthermia. The survival of dosed females was greater than that of the controls (29/50, 35/50, 44/50). Final mean body weights of mid- and high-dose males were 7% and 10% lower than that of the controls; final mean body weight of high-dose females was 11% lower than that of the controls. Final mean body weights of other dose groups were similar to those of the vehicle controls. At the 9-month interim evaluation, mean rectal temperature of males administered 40 mg/kg was significantly greater than that of the controls. Relative liver and kidney weights of males and females administered 20 or 40 mg/kg were significantly greater than those of controls. At the 15-month interim evaluation, relative liver weights of dosed females and absolute liver weights of 40 mg/kg females were significantly greater than those of the controls, as were relative liver and kidney weights of 40 mg/kg males. Pathology Findings: In the 2-year studies, administration of pentachloroanisole to males was associated with significant increases in the incidences of benign adrenal medulla pheochromocytomas. The incidence of benign adrenal medulla pheochromocytomas was marginally increased in high-dose females and slightly exceeded the range of the historical controls. Incidences of adrenal medulla hyperplasia were increased in dosed female rats, but not in dosed males. The incidences of pancreatic adenomas and focal hyperplasia were decreased in dosed males. The incidences of mammary gland fibroadenomas and uterine stromal polyps and sarcomas (combined) were decreased in high-dose females. Treatment-related increased incidences of intracytoplasmic pigmentation occurred in renal tubule epithelium, olfactory epithelium, and hepatocytes of males and females. Congestion and hemorrhage of the lungs, lymph nodes, thymus, adrenal cortex, and meninges, as well as hepatocellular centrilobular necrosis occurred almost exclusively in mid- and high-dose males that died or were killed moribund before the end of the studies. 2-YEAR STUDIES IN MICE: Based on the chemical-related mortality and liver lesions seen in the 16-day and 13-week studies, doses selected for the 2-year studies were 0, 20, and 40 mg/kg. Groups of 70 male and 70 female mice were administered pentachloroanisole in corn oil by gavage 5 days per week for up to 2 years. At 9 and 15 months, up to 10 animals per group were selected for interim evaluations. Survival, Body Weights, and Clinical Findings: The survival of dosed males was similar to that of the controls; survival of high-dose females was lower than that of the controls (24/50, 25/50, 16/50). The decreased survival of the high-dose females was attributed primarily to ovarian abscesses which were observed after moribund sacrifice. At the 9-month interim evaluation, the mean body weight of males administered 40 mg/kg was significantly lower than that of the vehicle controls. Absolute and relative liver weights of females and the relative liver weight of males administered 40 mg/kg were significantly greater than those of the controls. Final mean body weights of low- and high-dose males were 11% and 17% lower than that of the controls. Final mean body weights of dosed females were similar to that of the controls. There were no clinical findings attributed to pentachloroanisole administration. Pathology Findings: Centrilobular hepatocyte cytomegaly and pigment accumulation in hepatocytes and Kupffer cells were seen in dosed mice, but not in controls at the 9- and 15-month interim evaluations. In the 2-year studies, the incidence of benign pheochromocytomas was significantly increased in high-dose males. Dosed males also exhibited increased incidences of adrenal medulla hyperplasia and hypertrophy. The incidences of hemangiosarcomas of the liver were significantly increased in dosed males. Increased incidences of hepatocellular cytologic alteration, biliary tract hyperplasia, and Kupffer cell pigmentation occurred in dosed males and females; the incidences of mixed cell foci were also increased in dosed males. Cytologic alteration encompassed hepatocellular cytomegaly, karyomegaly, hepatocyte degeneration and necrosis, and multinucleated giant cell formation, and was considered an advanced stage of the pathologic process observed at 13 weeks. GENETIC TOXICOLOGY: Pentachloroanisole was mutagenic in Salmonella typhimurium strains TA98 and TA1537 in the absence but not in the presence of exogenous metabolic activation (S9). No clear mutagenic activity was observed in TA100 with hamster S9, without S9, or in TA1535 with or without S9. An equivocal response was observed in TA100 with rat S9. Pentachloroanisole was positive for induction of trifluorothymidine resistance in mouse lymphoma L5178Y cells with S9; the response observed without S9 was weak and inconsistent. In cytogenetic tests with Chinese hamster ovary cells, pentachloroanisole induced sister chromatid exchanges, but not chromosomal aberrations, with and without S9. TOXICOKINETICS: Male and female F344/N rats and B6C3F1 mice were administered 10, 20, or 40 mg/kg pentachloroanisole by gavage or 10 mg/kg pentachloroanisole intravenously (Appendix H). A rapid elimination of pentachloroanisole and a rapid formation of its main metabolite, pentachlorophenol, were seen in both species after an intravenous or an oral dose of pentachloroanisole. The area under the concentration-versus-time curve of pentachloroanisole increased with dosage in each species but the dose proportionality was lost above 20 mg/kg. No sex-related differences were found in the rate of absorption of pentachloroanisole from the GI tract, in the area under the concentration-versus-time curve, or in the overall rate elimination of pentachloroanisole. However, in female rats the area under the concentration-versus-time curve of pentachlorophenol was significantly larger than in male rats. No such difference was observed in mice. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of pentachloroanisole in male F344/N rats based on increased incidences of benign pheochromocytomas of the adrenal medulla. There was equivocal evidence of carcinogenic activity of pentachloroanisole in female F344/N rats based on marginally increased incidences of benign pheochromocytomas of the adrenal medulla. There was some evidence of carcinogenic activity of pentachloroanisole in male B6C3F1 mice based on increased incidences of benign pheochromocytomas of the adrenal medulla and hemangiosarcomas of the liver. There was no evidence of carcinogenic activity of pentachloroanisole in female B6C3F1 mice given doses of 20 or 40 mg/kg. Pentachloroanisole administration was associated with increased incidences of adrenal medulla hyperplasia in female rats and increased incidences of pigmentation in the renal tubule epithelium, olfactory epithelium, and hepatocytes of male and female rats. In addition, decreased incidences of pancreatic adenomas and focal hyperplasia in male rats and decreased incidences of mammary gland fibroadenomas and uterine stromal polyps and sarcomas (combined) in female rats were observed. Hyperthermia-related lesions in male rats receiving 20 or 40 mg/kg were considered indirectly related to pentachloroanisole administration. Pentachloroanisole administration was associated with increased incidences of adrenal medulla hyperplasia and hypertrophy and hepatocellular mixed cell foci in male mice. In male and female mice, nonneoplastic liver lesions associated with pentachloroanisole administration included hepatocellular cytologic alteration, Kupffer cell pigmentation, biliary tract hyperplasia, and subacute inflammation. Synonyms: 2,3,4,5,6-pentachloroanisole; methyl pentachlorophenate; methyl pentachlorophenyl ether; o-methylpentachlorophenol; pentachloromethoxybenzene; pentachlorophenyl methyl ether

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Ethylene Glycol (CAS No. 107-21-1) in B6C3F1 Mice (Feed Studies).

Ethylene glycol is a major constituent of motor vehicle antifreeze-coolant fluids and is also found in other commercial products including hydraulic brake fluids, adhesives, printer's inks, and wood stains. It is used in the manufacture of polyester films and fibers, polyethylene terephthalate (PET) solid state resins, plasticizers, elastomers, cellophane, and other products. Previous 13-week and 2-year studies of ethylene glycol in F344 rats were considered adequate to evaluate the toxicology and carcinogenicity of ethylene glycol in this species and strain; therefore, the present studies were conducted in mice only. Toxicology and carcinogenesis studies were conducted by administering ethylene glycol (greater than 99% pure) in feed to male and female B6C3F1 mice for 13 weeks and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse lymphoma L5178Y cells, and Chinese hamster ovary cells. 13-Week Studies: Groups of 10 male and 10 female mice received feed containing 0, 3,200, 6,300, 12,500, 25,000 or 50,000 ppm ethylene glycol. All mice survived to the end of the studies. Final mean body weights of dosed male and female mice and feed consumption of dosed males were similar to those of the controls. Feed consumption of dosed females was significantly greater than that of controls. Absolute and relative organ weights of mice administered ethylene glycol were generally similar to those of controls throughout the study. No chemical-related clinical findings were observed. Chemical-related kidney and liver lesions, seen only in 25,000 and 50,000 ppm male mice, consisted of nephropathy and centrilobular hepatocellular hyaline degeneration (cytoplasmic accumulation of non-birefringent, eosinophilic, globular, or crystalline material resembling erythrocyte fragments). 2-Year Studies: Groups of 60 mice received diets containing ethylene glycol for up to 103 weeks (males: 0, 6,250, 12,500, or 25,000 ppm; females: 0, 12,500, 25,000, or 50,000 ppm). These concentrations correspond to daily doses of approximately 1,500, 3,000, or 6,000 mg/kg body weight for male mice and 3,000, 6,000, or 12,000 mg/kg for females. Dietary concentrations greater than 50,000 ppm have the potential to affect the nutritional value of the feed. Interim evaluations were performed on six males and nine or ten females from each dose group at 15 months. Survival, Body Weights, Feed Consumption, and Clinical Findings in the 2-Year Studies: At the end of the 2-year studies, survival rates of male and female mice exposed to ethylene glycol were similar to those of controls. Mean body weights and feed consumption of exposed male and female groups were also similar to those of controls. No clinical findings associated with the administration of ethylene glycol were observed. Pathology Findings: No chemical-related neoplasms were observed in male or female mice in these studies. Hepatocellular hyaline degeneration was seen in mid- and high-dose male and high-dose female mice. Pulmonary arterial medial hyperplasia was observed at an increased incidence in exposed females but not in exposed males. Incidence and severity of nephropathy were not affected by treatment in either sex. Small numbers of oxalate-like crystals, calculi, or both were noted in renal tubules, urethrae, and/or urinary bladders in a few high-dose male mice. Genetic Toxicology: Ethylene glycol did not induce gene mutations in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537, trifluorothymidine resistance in mouse L5178Y lymphoma cells, or sister chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells. All tests were conducted with and without exogenous metabolic activation (S9). Conclusions: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of ethylene glycol in male B6C3F1 mice receiving 6,250, 12,500, or 25,000 ppm, or in female B6C3F1 mice receiving 12,500, 25,000, or 50,000 ppm. Administration of ethylene glycol resulted in hepatocellular hyaline degeneration in male mice fed diets diets containing 12,500 or 25,000 ppm and in female mice fed diets containing 50,000 ppm. An increased incidence of medial hyperplasia of small pulmonary arteries and arterioles occurred in female mice fed diets containing 12,500, 25,000, or 50,000 ppm ethylene glycol. Synonyms: 1,2-dihydroxyethane; ethane-1,2-diol; 1,2-ethanediol; ethylene alcohol; ethylene dihydrate; glycol; glycol alcohol; 2-hydroxyethanol; monoethylene glycol

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Promethazine Hydrochloride (CAS No. 58-33-3) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Promethazine hydrochloride is a drug used for the management of allergic conditions, motion sickness and nausea, and as a sedative to (treat psychiatric disorders. This drug was nominated for testing by the Food and Drug Administration because of its widespread use in human medicine and because of lack of data on its potential carcinogenicity. Oral administration is the most common route of human exposure. Toxicology and carcinogenicity studies were conducted by administering promethazine hydrochloride (>99% pure) in distilled water by gavage to groups of male and female F344/N rats and B6C3F1 mice for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, in cultured Chinese hamster ovary cells, and in Drosophila melanogaster. 16-DAY STUDY IN RATS: Groups of five male and five female rats received 0, 18.5, 55.5, 166.5, 500, or 1,500 mg promethazine hydrochloride/kg body weight once daily, 5 days per week for a total of 12 doses in a 16-day period. All rats receiving 1,500 mg/kg, four males and four females receiving 500 mg/kg, and one male and one female receiving 166.5 mg/kg died during the study. No deaths occurred in the remaining dose groups. Final mean body weights of rats receiving 166.5 mg/kg were significantly lower (12% to 25%) than those of the controls. Clinical findings included decreased activity, ocular discharge, and labored breathing in males and females receiving 166.5, 500, and 1,500 mg/kg as well as tremors in females receiving 166.5 and 500 mg/kg. There were dose-related increases in the absolute and relative liver weights of rats. Focal suppurative inflammation occurred in the nose of some male and female rats receiving 55 or 166.5 mg/kg and in the trachea of some male and female rats receiving 166.5 mg/kg. 16-DAY STUDY IN MICE: Groups of five male and five female mice received 0, 18.8, 37.5, 75, 150, or 300 mg promethazine hydrochloride/kg body weight once daily, 5 days per week for a total of 12 doses in a 16-day period. Two females receiving 75 mg/kg, one male and one female receiving 150 mg/kg, and four females receiving 300 mg/kg died during the study. No deaths occurred in the remaining dose groups. Final mean body weights of mice receiving promethazine hydrochloride were similar to those of the controls. However, in male and female controls, the final mean body weights were 11% to 12% lower than the initial mean body weights. Clinical findings occurred as early as the first day of the study and included decreased activity in male and female mice receiving 150 and 300 mg/kg. Tremors occurred in one male and five females in the 300 mg/kg group on day 1 and in one male in the 150 mg/kg group and five males and one female in the 300 mg/kg group on day 2. Absolute and relative liver weights of male mice receiving 75, 150, or 300 mg/kg were significantly greater than those of the controls. No chemical related lesions were present in male or female mice. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats received 0, 3.7, 11.1, 33.3, 100, or 300 mg promethazine hydrochloride/kg body weight once daily, 5 days per week for 13 weeks. One female receiving 100 mg/kg and six males and nine females receiving 300 mg/kg died during the study. No deaths occurred in the remaining dose groups. Final mean body weights of male rats receiving 100 or 300 mg/kg were significantly lower (19% to 22%) than those of the controls. Mean body weight gain of females receiving 100 mg/kg was significantly lower (14%) than that of the controls. Clinical findings in rats included hunched posture and labored breathing. Absolute and relative liver weights of males receiving 11.1, 33.3, 100, or 300 mg/kg and females receiving 33.3 or 100 mg/kg were significantly greater than those of the controls. Focal suppurative inflammation of the nose and trachea occurred with an increased incidence in rats receiving 100 and 300 mg/kg. A dose-related increased incidence of vacuolar degeneration of the nasal olfactory epithelium occurred in male and female rats that received 11.1, 33.3, or urred in male and female rats that received 11.1, 33.3, or 100 mg/kg. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice received 0, 5, 15, 45, 135, or 405 mg promethazine hydrochloride/kg body weight once daily, 5 days per week for 13 weeks. One control female, one female receiving 5 mg/kg, two females receiving 45 mg/kg, four females receiving 135 mg/kg, and all mice receiving 405 mg/kg died during the study. No deaths occurred in the remaining dose group. Final mean body weights of mice receiving 135 mg/kg were significantly lower (8% to 9%) than those of the controls. Clinical findings of toxicity included labored breathing and decreased activity in one 135 mg/kg female. Absolute and relative liver weights increased in a dose-related trend in both sexes. No chemical-related lesions were observed in mice. 2-YEAR STUDY IN RATS: Based on mortality and body weight differences observed at higher levels, doses of promethazine hydrochloride selected for the 2-year study in rats were 0, 8.3, 16.6, and 33.3 mg/kg. Groups of 60 male or 60 female rats were administered promethazine hydrochloride in deionized water by gavage once daily, 5 days per week for up to 103 weeks. Up to ten male and ten female rats per dose group were evaluated at 15 months. Survival, Body Weights, and Clinical Findings: There was a significant dose-related decrease in survival of rats. The survival rates in the 16.6 and 33.3 mg/kg male groups and in the 33.3 mg/kg female group were significantly lower than those of the controls. The final mean body weight of male rats receiving 33.3 mg/kg promethazine hydrochloride was 10% lower than that of the controls. Final mean body weights of female rats in the 16.6 and 33.3 mg/kg groups were 9% and 11% lower than that of the controls, respectively. No chemical-related clinical findings were noted in any dose group. Significant increases in the absolute and relative liver weights of mid- and high-dose female rats and the relative liver weights of mid- and high-dose male rats were observed at the 15-month interim evaluation. There were no biologically significant differences in the hematology or clinical chemistry parameters measured at 15 months. Pathology Findings: No neoplasms that could be attributed to promethazine hydrochloride administration were found in male or female rats. Several neoplasms occurred with a significantly decreased incidence in rats receiving promethazine hydrochloride. These included adrenal medullary pheochromocytoma (benign or malignant) and pituitary gland adenoma in the 33.3 mg/kg males and uterine stromal polyp in the 33.3 mg/kg females. The decreased incidences of adrenal medullary pheochromocytoma were chemical related. The decreased incidences of pituitary gland adenoma and uterine stromal polyp may have been related to chemical administration. Diffuse fatty change of the liver of male rats increased with dose and was attributed to chemical administration. 2-YEAR STUDY IN MICE: Based on mortality and body weight differences observed at higher levels, the doses of promethazine hydrochloride selected for the 2-year study were 0, 11.25, 22.5, and 45 mg/kg for male mice and 0, 3.75, 7.5, and 15 mg/kg for female mice. Groups of 60 male or 60 female mice were administered promethazine hydrochloride in deionized water by gavage once daily, 5 days per week for up to 103 weeks. Up to 10 male and 10 female mice per dose group were evaluated at 15 months. Survival, Body Weights, and Clinical Findings: Survival of mice receiving promethazine hydrochloride was similar to that of the controls. Mean body weights of mice were within 7% of those of the controls throughout the study. There were no chemical-related clinical findings in male or female mice. There were no differences in hematology or clinical chemistry parameters measured at 15 months that were attributed to the administration of promethazine hydrochloride. Pathology Findings: There were no neoplasms or nonneoplastic lesions that were attributed to the administration of promethazine hydrochloride. GENETIC TOXICOLOGY: Promethazine hydrochloride did not induce gene mutations in Salmonella typhimurium strains TA97, TA98, TA100, TA1535, or TA1537, or a significant increase in chromosomal aberrations in cultured Chinese hamster ovary cells; both of these tests were conducted with and without exogenous metabolic activation (S9). A small dose-related increase in sister chromatid exchanges was observed in cultured Chinese hamster ovary cells in the presence of S9; this response was considered to be equivocal. No increase in sister chromatid exchanges was observed in the absence of S9. Promethazine hydrochloride did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster administered the chemical by feeding or injection. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of promethazine hydrochloride in male or female F344/N rats receiving 8.3, 16.6, or 33.3 mg/kg. There was no evidence of carcinogenic activity of promethazine hydrochloride in male B6C3F1 mice receiving 11.25, 22.5, or 45 mg/kg. There was no evidence of carcinogenic activity of promethazine hydrochloride in female B6C3F1 mice receiving 3.75, 7.5, or 15 mg/kg. The decrease in the incidences of adrenal medullary pheochromocytoma in male rats was considered to be related to promethazine hydrochloride administration. The decrease in the incidences of pituitary gland adenoma in male rats and uterine stromal polyp in female rats may have been related to promethazine administration. Synonyms: Phenothiazine,10-(2-(dimethylamino)propyl)-,monochlorohydrate; 10H-phenothiazine-10-ethanamine;10-(2-dimethylamino-2-methylethyl)phenothiazine hydrochloride; N-(2 -dimethylamino-2 -methyl)ethylphenothiazine hydrochloride Trade names: Diprazi; Kinetosin; Phenergan; Phenergan hydrochloride; Promine; Pipolfen; Plletia; Prorex; Promantine; Pyrethia; Romergan hydrochlonde

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of 3,4-Dihydrocoumarin (CAS No. 119-84-6) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

3,4-Dihydrocoumarin was nominated by the Food and Drug Administration and the National Cancer Institute for study because of its widespread use as a flavoring agent in beverages, gelatins, puddings, candy, and other food items; as a fragrance in perfumes, creams, and cosmetics; and because of interest in the structure-activity relationships of the coumarin derivatives. Toxicity and carcinogenicity studies were conducted by administering 3,4-dihydrocoumarin (99% pure) in corn oil by gavage to groups of male and female F344/N rats and B6C3F1 mice for 16 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and peripheral blood cells of mice. 16-DAY STUDY IN RATS: Groups of five male and five female rats received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 190, 375, 750, 1,500, or 3,000 mg/kg body weight 5 days per week for a total of 12 doses in a 16-day period. All male and female rats given 3,000 mg/kg, and four male rats and five female rats given 1,500 mg/kg died. Body weight gains and final mean body weights of rats receiving 190, 375, or 750 mg/kg were similar to those of the controls. There were no clinical findings of organ-specific toxicity or evidence of impaired blood coagulation. 16-DAY STUDY IN MICE: Groups of five male and five female mice received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 140, 280, 560, 1,125, or 2,250 mg/kg body weight 5 days per week for a total of 12 doses in a 16-day period. All mice given 2,250 mg/kg died. Body weight gains and final mean body weights of mice receiving 140, 280, 560, and 1,125 mg/kg were similar to those of the controls. There were no clinical findings of organ-specific toxicity or evidence of impaired blood coagulation. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 75, 150, 300, 600, or 1,200 mg/kg body weight 5 days per week for 13 weeks. Two male rats and five female rats given 1,200 mg/kg died. The body weight gain and final mean body weight of male rats that received 1,200 mg/kg were significantly lower than those of the controls, but the final mean body weights of other dosed groups of male rats and all dosed groups of female rats were similar to or slightly greater than those of the controls. Platelet counts were significantly lower in males and females receiving 600 and 1,200 mg/kg and in females receiving 300 mg/kg. Hemoglobin and hematocrit values and erythrocyte counts were significantly lower in males that received 300 mg/kg or more. The absolute and relative liver and kidney weights of males and females receiving 600 and 1,200 mg/kg were significantly greater than those of the controls. Hepatocellular hypertrophy was observed in rats given 300, 600, and 1,200 mg/kg. The high dose selected for the 2-year study was 600 mg/kg, which was below the level at which mortality, lower final mean body weights, and treatment-related liver lesions were observed. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 100, 200, 400, 800, or 1,600 mg/kg body weight 5 days per week for 13 weeks. Eight male and five female mice receiving 1,600 mg/kg died. Deaths in other groups were attributed to dosing accidents. Final mean body weights of dosed male and female mice were similar to those of the controls, and there were no treatment-related changes in any hematologic parameters. The absolute and relative liver weights of males and females that received 1,600 mg/kg and the relative kidney weight of males that received 1,600 mg/kg were significantly greater than those of the controls. No treatment-related lesions were noted. The high dose selected for the 2-year study was 600 mg/kg, which was below the level at which mortality, lower final mean body weights, and treatment-related liver lesions were observed. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats received 3,4-dihydrocoumarin in corn oil by gavage at age at doses of 0, 150, 300, or 600 mg/kg body weight. After 15 months, up to 10 animals from each group were evaluated. Survival, Body Weights, and Clinical Findings: Survival rates of dosed male rats were lower than that of the controls (O mg/kg, 28/51; 150 mg/kg, 12/50; 300 mg/kg, 8/50; 600 mg/kg, 2/50) but survival rates of dosed female rats were similar to that of the controls (31/50, 21/51, 26/50, 23/51). The decreased survival in dosed male rats was attributed to a chemical-related increase in the severity of nephropathy. The final mean body weight of male rats receiving 600 mg/kg was lower than that of the controls, but the final mean body weights of other dosed groups of male rats and all dosed groups of female rats were similar to those of the controls. No clinical findings related to chemical administration were observed. Hematology and Clinical Chemistry: At the 15-month interim evaluation, the hemoglobin concentrations, mean erythrocyte volumes, or mean erythrocyte hemoglobin concentrations in the 300 and 600 mg/kg female rats were slightly, but significantly, lower than those of the controls. In males, only the hemoglobin concentration in the 600 mg/kg group was significantly lower. Serum levels of alkaline phosphatase, alanine aminotransferase, sorbitol dehydrogenase, or g-glutamyltransferase in the 300 and 600 mg/kg male rats were significantly higher than those in the controls. In females, alkaline phosphatase and g-glutamyltransferase levels were significantly higher in the 600 mg/kg group. Pathology Findings: The principal lesions associated with the administration of 3,4-dihydrocoumarin to rats occurred in the kidney and forestomach. There was a chemical related increase in the severity of nephropathy in all dosed male rats and in 300 and 600 mg/kg female rats. There was a corresponding increased incidence of parathyroid gland hyperplasia, probably as a result of compromised renal function. In the standard evaluation of single kidney sections, renal tubule adenomas were observed in one 150 and two 600 mg/kg males and one each in the control, 150, and 300 mg/kg females. Transitional cell carcinomas were also observed in two 600 mg/kg male rats. However, an extended evaluation of step sections identified significantly higher incidences of focal hyperplasia and adenoma in the 600 mg/kg males than in controls (hyperplasia: 0/50, 5/48, 6/47, 8/50; adenoma: 1/50,1/48, 3/47, 6/50). The incidence of forestomach ulcers in all groups of dosed male rats was significantly greater than that of the controls (4/47, 14/48, 20/50, 16/46). STOP-EXPOSURE EVALUATION: A group of 40 male rats received 600 mg/kg 3,4-dihydrocoumarin in corn oil by gavage for 9 months, when 20 of the animals were necropsied and evaluated. The remainder of the male rats received only the corn oil vehicle until they died or until the end of the study. Similarly, a group of 30 male rats received 600 mg/kg 3,4-dihydrocoumarin in corn oil by gavage for 15 months, when 10 of the rats were necropsied and evaluated. The remaining 20 rats received only corn oil until the end of the study. A group of 20 vehicle control male rats was necropsied at 9 months, and another 10 vehicle control male rats were necropsied at 15 months. The severity of nephropathy in male rats of the stop-exposure groups was significantly greater than that of males examined at the 9- and 15-month interim evaluations. This was expected because nephropathy is a progressive degenerative disease that naturally increases in severity with age. 2-YEAR STUDY IN MICE: Groups of 70 male and 70 female mice received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 200, 400, or 800 mg/kg body weight. After 15 months, five to 10 animals from each group were evaluated. Additional groups of 8 to 10 animals were evaluated for clinical pathology after 15 months. Survival, Body Weights, and Clinical Findings Survival rates of dosed male and female mice were similar to those of the controls (males: O mg/kg, 42/50; 200 mg/kg, 39/51; 400 mg/kg, 34/51; 800 mg/kg, 38/50; females: 36/51, 39/50, 41/50, 28/52). Final mean body weights of dosed male and female mice were similar to those of the controls. No clinical findings were noted that were related to chemical administration. Hematology and Clinical Chemistry: There were no differences in hematology or clinical chemistry parameters that were considered to be chemical related. Pathology Findings: The principal neoplasms associated with the administration of 3,4-dihydrocoumarin to mice occurred in the liver. There were significantly increased incidences of hepatocellular adenomas in all groups of dosed female mice. Further, the incidences of multiple hepatocellular adenomas in dosed female mice were greater than that of the controls (control, 0/51; 200 mg/kg, 6/50; 400 mg/kg, 9/50; 800 mg/kg, 9/52). However, there was no corresponding increased incidence of hepatocellular carcinoma in dosed female mice (3/51, 2/50, 4/50, 6/52), and the incidences of hepatocellular adenoma or carcinoma were similar between dosed and control male groups (adenoma: 29/50, 23/51, 36/51, 31/50; carcinoma: 11/50, 11/51, 11/51, 6/50). The incidence of alveolar/bronchiolar adenoma in the 200 and 400 mg/kg male mice was marginally greater than that of the controls (8/50,15/50,15/51,10/50). However, these neoplasms were not considered chemical related because the increased incidence was slight and there was no corresponding increased incidence in the 800 mg/kg group. The incidence of alveolar/bronchiolar neoplasms in female mice was similar between the dosed and control groups (adenoma: 2/51, 5/50, 1/48, 3/51; carcinoma: 0/51, 1/50, 0/48, 0/51). In the standard evaluation of single sections of kidney, focal hyperplasia and adenoma or carcinoma of the renal tubule were identified in several dosed male mice, but not in controls [adenoma or carcinoma (combined): 0/50,1/51, 2/51,1/49; hyperplasia: 2/50, 2/51, 5/51, 2/49]. In an extended evaluation of step sections, a few additional males with focal hyperplasia or renal tubule adenomas were identified in the dosed groups. However, the incidences of these lesions in dosed groups of male mice were not significantly greater than those of the controls, and did not increase with dose (hyperplasia: 0/50,1/51, 3/51, 1/49; renal tubule adenoma: 0/50, 0/51, 2/51, 1/49). Therefore, the low number of renal tubule neoplasms in male mice was not considered to be chemical related. GENETIC TOXICOLOGY: 3,4-Dihydrocoumarin did not induce gene mutations in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 with or without exogenous metabolic activation (S9). It induced sister chromatid exchanges but not chromosomal aberrations in cultured Chinese hamster ovary cells, with and without S9. No induction of micronuclei was noted in peripheral blood erythrocyte samples obtained from male and female B6C3F1 mice at the end of the 13-week toxicology study. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of 3,4-dihydrocoumarin in male F344/N rats based on increased incidences of renal tubule adenomas and focal hyperplasia. The transitional cell carcinomas in two 600 mg/kg males may also have been chemical related. There was no evidence of carcinogenic activity of 3,4-dihydrocoumarin in female F344/N rats receiving 150, 300, or 600 mg/kg. There was no evidence of carcinogenic activity of 3,4-dihydrocoumarin in male B6C3F1 mice receiving 200, 400, or 800 mg/kg. There was some evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined). 3,4-Dihydrocoumarin caused ulcers, hyperplasia, and inflammation of the forestomach, parathyroid gland hyperplasia, and increased severity of nephropathy in male rats. Synonyms: 1,2-benzodihydropyrone, 2H-1-benzopyran-2-one, 2-chromanone, 3,4-dihydro-2H-1-benzopyran-2-one, dihydrocoumarin, hydrocoumarin, o-hydroycinnamic acid, delta-lactone-hydrocinnamic acid, melilotin, melilotine, melilotol, 2-oxochroman

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Coumarin (CAS No. 91-64-5) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Coumarin is the basic structure of numerous naturally occurring compounds with important and diverse physiological activities. More than a thousand coumarin derivatives have been described, varying from simple coumarins containing alkyl and hydroxyl side chains to complex coumarins with benzoyl, furanoyl, pyranoyl, or alkylphosphorothionyl substituents. Coumarin and 3,4-dihydrocoumarin were nominated by the Food and Drug Administration and the National Cancer Institute for study because of the widespread use of coumarin in perfumes, cosmetics, and other products as a fragrance, continued interest in coumarin compounds as flavor-enhancing agents for foods, and the interest in structure-activity relationships of this important group of compounds. Coumarin is believed to be metabolized to a 3,4-epoxide intermediate, which may be responsible for its toxic effects, while 3,4-dihydrocoumarin, which lacks the 3,4-double bond, is not considered likely to form an epoxide intermediate. Toxicity and carcinogenicity studies were conducted by administering coumarin (97% pure) in corn oil by gavage to groups of male and female F344/N rats and B6C3F1 mice for 16 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and B6C3F1 mice. 16-DAY STUDY IN RATS: Groups of five male and five female rats received coumarin in corn oil by gavage at doses of 0, 25, 50, 100, 200, or 400 mg per kg body weight, 5 days a week for a total of 12 doses in a 16-day period. All female rats and four male rats receiving 400 mg/kg died. The mean body weight gains and final mean body weights of surviving dosed male and female rats were similar to those of the controls. There were no clinical signs of organ-specific toxicity, and there was no evidence of impaired blood coagulation from measurements of capillary clotting time or prothrombin and activated partial thromboplastin time. 16-DAY STUDY IN MICE: Groups of five male and five female mice received coumarin in corn oil by gavage at doses of 0, 40, 75, 150, 300, or 600 mg per kg body weight, 5 days a week for a total of 12 doses in a 16-day period. All mice receiving 600 mg/kg, two male mice receiving 300 mg/kg, and one male mouse receiving 75 mg/kg died. The mean body weight gains and final mean body weights of surviving dosed male and female mice were similar to those of the controls. Clinical findings of inactivity, excessive lacrimation, piloerection, bradypnea, ptosis, or ataxia were observed in some mice from the 300 and 600 mg/kg groups within the first several hours after dosing. Capillary clotting time and platelet counts of dosed mice were similar to those of controls. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats received coumarin in corn oil by gavage at doses of 0,19, 38, 75,150, or 300 mg per kg body weight. Three male and three female rats receiving 300 mg/kg died. The mean body weight gains and final mean body weights of male rats that received 150 and 300 mg/kg were significantly lower than those of the controls. There were no clinical signs related to specific organ toxicity. Male and female rats receiving coumarin exhibited dose-related decreases in mean erythrocyte volume and mean erythrocyte hemoglobin, and dose-related increases in erythrocyte counts. Serum levels of total bilirubin and one or more cytoplasmic enzymes including alanine aminotransferase, aspartate aminotransferase, ornithine carbamoyltransferase, and/or sorbitol dehydrogenase in males and females receiving 300 mg/kg were higher than those of controls. The absolute and relative liver weights of male and female rats that received 150 and 300 mg/kg were significantly greater than those of the controls. Centrilobular hepatocellular degeneration and necrosis, chronic active inflammation, and bile duct hyperplasia were observed in the liver of rats receiving 150 or 300 mg/kg. The high dose selected for the 2-year study was 100 mg/kg, which was just below the level at which mortality, lower final mean body weiody weights, and treatment-related liver lesions were observed in the 13-week study. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice received coumarin in corn oil by gavage at doses of 0, 19, 38, 75, 150, or 300 mg per kg body weight. Two male mice receiving 300 mg/kg died. The mean body weight gain and final mean body weight of surviving male mice that received 300 mg/kg were significantly lower than those of the controls. No clinical signs of toxicity were observed. Male and female mice receiving coumarin exhibited dose-related decreases in mean erythrocyte volume and mean erythrocyte hemoglobin. The absolute and relative liver weights of males and females that received 150 and 300 mg/kg were significantly greater than those of the controls. Centrilobular hepatocellular hypertrophy was observed in male and female mice receiving 300 mg/kg. The high dose selected for the 2-year study was 200 mg/kg, which was just below the level at which mortality and liver lesions were observed in the 13-week study. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats were administered coumarin in corn oil by gavage at doses of 0, 25, 50, or 100 mg per kg body weight. After 15 months, 10 animals from each group were evaluated. Survival, Body Weights, and Clinical Findings: None of the male rats receiving 100 mg/kg and only two males receiving 50 mg/kg survived until the end of the study (vehicle control, 28/50; 25 mg/kg, 9/50; 50 mg/kg, 2/51; 100 mg/kg, 0/50). Survival of dosed female rats was similar to that of the controls (29/50, 38/50, 36/50, 30/50). The reduced survival in dosed male rats was primarily attributed to chemical-related exacerbation of spontaneously occurring renal disease. Final mean body weights of female rats that received 100 mg/kg and all dosed groups of male rats were lower than those of the controls. There were no clinical signs of toxicity in rats, other than nonspecific signs relating to debilitation as a result of renal or other spontaneous disease. Hematology and Clinical Chemistry: At the 15-month interim evaluation, the values for one or more hematologic parameters including mean erythrocyte volume, mean erythrocyte hemoglobin in 50 and 100 mg/kg rats, and hematocrit or hemoglobin in 100 mg/kg rats were significantly lower than those of controls. Activated partial thromboplastin times were also significantly lower in 50 and 100 mg/kg males, while platelet counts were significantly higher. Activities of alanine aminotransferase, sorbitol dehydrogenase, or g-glutamyltransferase in 50 and 100 mg/kg male and 100 mg/kg female rats were significantly higher than those of the controls at the 15-month interim evaluation. Pathology Findings: The principal lesions associated with the administration of coumarin to rats for up to 2 years occurred in the liver, kidney, and forestomach. While the hepatic lesions were seen in all groups of males, they occurred only in the 50 and 100 mg/kg females. The lesions consisted of a spectrum of changes including hepatocellular necrosis, fibrosis, cytologic alteration, and increased severity of bile duct hyperplasia. The incidences of hepatocellular neoplasms were not increased in dosed rats. There was a chemical-related increase in the average severity of nephropathy in all groups of dosed male and female rats. There were corresponding increased incidences of parathyroid gland hyperplasia in all groups of dosed males, probably as a result of compromised renal function. In the standard evaluation of single kidney sections, a low incidence of renal adenomas was seen in all groups of males and in 100 mg/kg females (males: vehicle control, 1/49; 25 mg/kg, 2/50; 50 mg/kg, 2/51; 100 mg/kg, 1/50; females: 0/49, 0/50, 0/50, 2/49). An evaluation of step sections identified additional individuals with renal tubule focal hyperplasia (males: 2/49, 12/50, 10/51, 6/50; females: 1/49, 0/50, 4/50, 2/49) and adenoma (males: 0/49, 4/50, 5/51, 4/50; females: 0/49, 0/50, 1/50,1/49) in the dosed groups. The incidences of forestomach ulcers in all groups of dosed male rats and in 100 mg/kg female rats were significantly greater than those of the controls (males: 7/48, 24/50, 35/51, 34/50; females: 1/48, 1/49, 6/50, 9/48). STOP-EXPOSURE EVALUATION: A group of 40 male rats received 100 mg/kg coumarin in corn oil by gavage for 9 months, when 20 of the animals were necropsied and evaluated. The remainder of the male rats received only the corn oil vehicle during the 15-month recovery period. Similarly, a group of 30 male rats received 100 mg/kg coumarin in corn oil by gavage for 15 months, when 10 of the rats were necropsied and evaluated. The remaining 20 rats received only corn oil during the 9-month recovery period. A group of 20 vehicle control male rats were necropsied at 9 months, and another 10 vehicle control male rats were necropsied at 15 months. While chemical-related hepatic lesions were seen at both the 9- and 15-month interim evaluations, the incidences and severities of these lesions following the recovery period were generally similar to controls. Thus, the hepatic lesions produced by 9 or 15 months of exposure were reversible. In contrast to the liver lesions, the severity of nephropathy in male rats following the recovery period was significantly greater than that of males examined at the 9- and 15-month interim evaluations. This is not unexpected, since nephropathy is a progressive degenerative disease that naturally increases in severity with age. The incidence of renal tubule hyperplasia in the 15-month stop-exposure group (dosed for 15 months followed by the recovery period) and the incidence of renal tubule adenoma in the 9-month stop-exposure group were significantly greater than those of the control group. 2-YEAR STUDY IN MICE: Groups of 70 male and 70 female mice were administered coumarin in corn oil by gavage at doses of 0, 50, 100, or 200 mg per kg body weight for up to 2 years. After 15 months, 19 or 20 mice from each group were evaluated. Survival, Body Weights, and Clinical Findings: Survival of dosed male and female mice was similar to that of the controls (males: vehicle control, 43/50; 50 mg/kg, 47/50; 100 mg/kg, 42/50; 200 mg/kg, 37/51; females: 33/50, 40/50, 42/51, 28/51). The mean body weights of 200 mg/kg male and female mice were lower than those of controls throughout much of the study. There were no clinical findings related to chemical administration. Hematology and Clinical Chemistry: Mean erythrocyte volume, mean erythrocyte hemoglobin, and hematocrit of 200 mg/kg males and mean erythrocyte volume of 200 mg/kg females were significantly lower than those of the controls. Blood platelet counts of 200 mg/kg males and females were significantly higher than those of controls. There were no biologically significant differences in enzyme activities between dosed and control mice. Pathology Findings: The principal toxic lesions associated with the administration of coumarin to mice occurred in the liver. The incidences of centrilobular hypertrophy in 100 and 200 mg/kg males and 200 mg/kg females were significantly greater than those of controls. The incidences of syncytial alteration in all male dose groups and in 200 mg/kg females were also significantly greater than controls. The incidences of eosinophilic foci, a putative preneoplastic lesion, and of hepatocellular adenoma were significantly greater in the 50 and 100 mg/kg females. Hepatocellular carcinomas occurred with low incidences in the dosed females, but none occurred in the controls. The overall incidence of hepatocellular neoplasms (benign and malignant combined) in the 50 and 100 mg/kg females (control, 8/50; 50 mg/kg, 27/49; 100 mg/kg, 31/51; 200 mg/kg, 13/50) exceeds the range in historical controls (range 2%-34%; 129/898, 14.4%) from recent NTP studies. The reason for a lack of liver response in 200 mg/kg female mice is not known, but may be due in part to the decrease in body weight. While the incidences of eosinophilic foci were marginally greater in dosed male mice, the incidences of hepatocellular neoplasms were similar among the dosed and control groups. The incidences of alveolar/bronchiolar adenomas were significantly greater in 200 mg/kg male and female mice than in the controls. Further, the incidence of alveolar/bronchiolar carcinoma in 200 mg/kg females was also significantly greater than in controls. The overall incidence of pulmonary neoplasms (benign and malignant combined) in the 200 mg/kg groups (males: 14/50, 9/50,15/50, 25/51; females: 2/51, 5/49, 7/49, 27/51) exceeds the range in historical controls (males: range 6%-28%; 166/900, 18.4%; females: range 0%-14%; 58/899, 6.5%) from recent NTP studies. The incidence of squamous cell papilloma of the forestomach in 50 mg/kg males was greater than that of the controls (2/50, 8/50, 2/50, 0/51) and also exceeds the range of this neoplasm in control male mice from recent NTP studies (range 0%-14%; 27/902, 3.0%). The incidence of squamous cell papilloma of the forestomach in 50 mg/kg female mice was also slightly increased (1/52, 5/50, 2/51, 2/51); however, the incidence did not exceed the NTP historical range (27/901, 3%; range, 0%-10%). GENETIC TOXICOLOGY: Coumarin induced gene mutations in Salmonella typhimurium strain TA100 in the presence, but not in the absence, of exogenous metabolic activation (S9); no mutations were induced in strains TA98, TA1535, or TA1537, with or without S9. In Chinese hamster ovary cells, coumarin induced sister chromatid exchanges in the absence of S9, and chromosomal aberrations in the presence of S9. Coumarin did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster treated either as adults by feeding or injection, or as larvae by feeding. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood of male and female B6C3F1 mice administered coumarin by gavage for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year gavage studies there was some evidence of carcinogenic activity of coumarin in male F344/N rats based on increased incidences of renal tubule adenomas. There was equivocal evidence of carcinogenic activity of coumarin in female F344/N rats based on a marginally increased incidence of renal tubule adenomas. There was some evidence of carcinogenic activity of coumarin in male B6C3F1 mice based on the increased incidence of alveolar/bronchiolar adenomas. There was clear evidence of carcinogenic activity of coumarin in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenomas, alveolar/bronchiolar carcinomas, and hepatocellular adenomas. The marginally increased incidences of squamous cell papillomas of the forestomach in male and female mice receiving 50 mg/kg may have been related to coumarin administration. The administration of coumarin to rats was also associated with an increased severity of nephropathy in the kidney and of bile duct hyperplasia in the liver, increased incidences of ulcers of the forestomach, and necrosis, fibrosis, and cytologic alteration of the liver. Administration of coumarin to mice was also associated with centrilobular hypertrophy, syncytial alteration, and eosinophilic focus in the liver. Synonyms: 5,6-benzo-alpha-pyrone, 2H-1-benzopyran-2-one, 2H-benzolblpyran-2-one, 1,2-oxo-1,2-benzopyran, 1,2-benzopyrone, cis-o-coumarinic acid lactone, coumarinic anhydride, cumarin, o-hydroxycinnamic acid lactone, kumarin, [2-propenoic acid, 3-(-2-hydroxyphenyl)-delta-lactone], Rattex, tonka bean camphor

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Talc (CAS No. 14807-96-6)(Non-Asbestiform) in F344/N Rats and B6C3F1 Mice (Inhalation Studies).

Talc ore may contain several other minerals including calcite, dolomite, magnesite, tremolite, anthophyllite, antigorite, quartz, pyrophyllite, micas, or chlorites. Talc products are sold in a multitude of grades which have physical or functional characteristics especially suited for particular applications, so occupational and consumer exposures to talc are complex. Epidemiology studies have suggested an association between non-fibrous talc and lung cancer risk. Talc was nominated by the National Institute of Occupational Safety and Health (NIOSH) for study by the NTP because of widespread human exposure and because of the lack of adequate information on its chronic toxicity and potential carcinogenicity. Toxicology and carcinogenicity studies of talc (non-asbestiform, cosmetic grade), a finely powdered hydrous magnesium silicate, were conducted by exposing groups of F344/N rats to aerosols for 6 hours per day, 5 days per week for up to 113 weeks (males) or 122 weeks (females). Groups of B6C3F1 mice were exposed similarly for up to 104 weeks. LIFETIME STUDY IN RATS: Groups of 49 or 50 male and 50 female rats were exposed to aerosols of 0, 6, or 18 mg/m(3) talc until mortality in any exposure group reached 80% (113 weeks for males and 122 weeks for females). These exposures were selected based on 4-week inhalation studies of the terminal lung talc burden in F344/N rats; concentrations greater than 18 mg/m(3) were expected to overwhelm lung clearance mechanisms and impair lung function. These exposure concentrations provided a dose equivalent of 0, 2.8, or 8.4 mg/kg per day for male rats and 0, 3.2, or 9.6 mg/kg per day for female rats. In a special study, additional groups of 22 male and 22 female rats were similarly exposed and examined for interim pathology evaluations or pulmonary function tests after 6, 11, 18, and 24 months and lung biochemistry and cytology studies after 24 months. The talc aerosols had a median mass aerodynamic diameter of 2.7 mm in the 6 mg/m(3) chamber and a median diameter of 3.2 mm in the 18 mg/m(3) chamber, with geometric standard deviations of 1.9 mm. However, there was a 7-week period beginning at study week 11 during which the chamber concentration for the 18 mg/m(3) rats varied from approximately 30 to 40 mg/m(3) because of difficulties with the aerosol concentration monitoring system. Further, there was a 12-week period beginning at approximately week 70 during which there were difficulties in generating the talc aerosol, and the chamber concentrations for rats and mice were substantially lower than the target concentrations. Survival, Body Weights, and Clinical Findings: The survival of male and female rats exposed to talc was similar to that of the controls. Mean body weights of rats exposed to 18 mg/m(3) were slightly lower than those of controls after week 65. No clinical findings were attributed to talc exposure. Pathology Findings: Absolute and relative lung weights of male rats exposed to 18 mg/m(3) were significantly greater than those of controls at the 6-, 11-, and 18-month interim evaluations and at the end of the lifetime study, while those of female rats exposed to 18 mg/m(3) were significantly greater at the 11-, 18-, and 24-month interim evaluations and at the end of the lifetime study. Inhalation exposure of rats to talc produced a spectrum of inflammatory, reparative, and proliferative processes in the lungs. Granulomatous inflammation occurred in nearly all exposed rats and the severity increased with exposure duration and concentration. Hyperplasia of the alveolar epithelium and interstitial fibrosis occurred in or near foci of inflammation in many exposed rats, while squamous metaplasia of the alveolar epithelium and squamous cysts were also occasionally seen. Accumulations of macrophages (histiocytes), most containing talc particles, were found in the peribronchial lymphoid tissue of the lung and in the bronchial and mediastinal Iymph nodes. In female rats, the incidences of alveolar/bronchiolar adenoma, carcinoma, and adenoma or carcinoma (combined) in the 18 mg/m(8 mg/m(3) group were significantly greater than those of controls. The incidences of pulmonary neoplasms in exposed male rats were similar to those in controls. Minor alterations attributed to talc exposure were also observed in the upper respiratory tract. Hyperplasia of the respiratory epithelium of the nasal mucosa in males and accumulation of cytoplasmic, eosinophilic droplets in the nasal mucosal epithelium in male and female rats occurred with a concentration-related increased incidence in the exposed groups. Adrenal medulla pheochromocytomas [benign, malignant, or complex (combined)] occurred with a significant positive trend in male and female rats, and the incidences in the 18 mg/m(3) groups were significantly greater than those of controls. Although adrenal medulla hyperplasia occurred with similar frequency among exposed and control females, the incidences of hyperplasia in exposed males were significantly lower than in controls. Lung Talc Burden: Lung talc burdens of male and female rats exposed to 6 mg/m(3) were similar and increased progressively from 6 to 24 months. Lung talc burdens of females exposed to 18 mg/m(3) also increased progressively from 6 to 24 months, while those of males exposed to 18 mg/m(3) remained about the same after 18 months. Lung burdens were generally proportional to exposure concentration at each interim evaluation. Pulmonary Function, Bronchoalveolar Lavage, and Lung Biochemistry: In exposed male and female rats there was a concentration-related impairment of respiratory function which increased in severity with increasing exposure duration. The impairment was characterized by reductions in lung volume (total lung capacity, vital capacity, and forced vital capacity), lung compliance, gas exchange efficiency (carbon monoxide diffusing capacity), and nonuniform intrapulmonary gas distribution. After 24 months, males exposed to 6 mg/m(3) talc had a significant increase in beta-glucuronidase and polymorphonuclear leukocytes; males exposed 18 mg/m(3) had significant increases in b -glucuronidase, lactate dehydrogenase, alkaline phosphatase, and total protein in bronchoalveolar lavage fluid. All exposed females had significantly increased a-glucuronidase, lactate dehydrogenase, alkaline phosphatase, total protein, and polymorphonuclear leukocytes; 18 mg/m(3) females also had significantly increased glutathione reductase. Viability and phagocytic activity of macrophages recovered from lavage fluid were not affected by talc exposure. Total lung collagen was significantly increased in rats at both exposure concentrations after 24 months, while collagenous peptides in lavage fluid and the percentages of newly synthesized protein from females, but not males, were also significantly increased at the 6 or 18 mg/m(3) levels. In addition, lung proteinase activity, primarily cathepsin D-like activity, was significantly greater in exposed males and females. Rats exposed to talc also had significant increases in collagenous peptides and acid proteinase in lung homogenates. 2-YEAR STUDY IN MICE: Groups of 47 to 49 male and 48 to 50 female mice were exposed to aerosols containing 0, 6, or 18 mg/m(3) talc for up to 104 weeks. These exposures were selected based on 4-week inhalation studies of the terminal lung talc burden in B6C3F1 mice; concentrations greater than 18 mg/m(3) were expected to overwhelm lung clearance mechanisms and impair lung function. These exposure concentrations provide a dose equivalent of 0, 2, or 6 mg/kg per day for male mice and 0, 1.3, or 3.9 mg/kg per day for female mice. In a special study, additional groups of 39 or 40 male and 39 or 40 female mice similarly exposed were examined for interim pathology evaluations, lung biochemistry, and cytology studies after 6, 12, and 18 months of exposure. The talc aerosols had a median mass aerodynamic diameter of 3.3 mm with a geometric standard deviation of 1.9 mm in the 6 mg/m(3) chamber, and a median diameter of 3.6 mm with a geometric standard deviation of 2.0 mm in the 18 mg/m(3) chamber. Further, there was a 12-week period beginning at approximately week 70 during which there were difficulties in generating the talc aerosol, and the chamber concentrations for rats and mice were substantially lower than the target concentrations. Survival, Body Weights, and Clinical Findings: Survival and final mean body weights of male and female mice exposed to talc were similar to those of the controls. There were no clinical findings attributed to talc exposure. Pathology Findings: Inhalation exposure of mice to talc was associated with chronic active inflammation and the accumulation of macrophages in the lung. In contrast to rats, hyperplasia of the alveolar epithelium, squamous metaplasia, or interstitial fibrosis were not associated with the inflammatory response in mice, and the incidences of pulmonary neoplasms in exposed and control groups of mice were similar. Accumulations of macrophages (histiocytes) containing talc particles were also present in the bronchial Iymph node. In the upper respiratory tract, cytoplasmic alteration, consisting of the accumulation of cytoplasmic eosinophilic droplets in the nasal mucosal epithelium, occurred with a concentration-related increased incidence in exposed male and female mice. Lung Talc Burden: Lung talc burdens of mice exposed to 6 mg/m(3) were similar between males and females and increased progressively from 6 to 24 months, except for males at 18 months. The lung talc burdens of mice exposed to 18 mg/m(3) were also similar between the sexes at each interim evaluation. Although the talc burdens of males and females increased substantially from 6 to 24 months, the values at 12 and 18 months were similar. Generally, lung burdens of mice exposed to 18 mg/m(3) were disproportionately greater than those of mice exposed to 6 mg/m(3), suggesting that clearance of talc from the lung was impaired, or impaired to a greater extent, in mice exposed to 18 mg/m(3) than in mice exposed to 6 mg/m(3). Bronchoalveolar Lavage and Lung Biochemistry: Increases in total protein, beta-glucuronidase, lactate dehydrogenase, glutathione reductase, total nucleated cells, and polymorphonuclear leukocytes in bronchoalveolar lavage fluid were observed primarily in mice exposed to 18 mg/m(3), although some parameters were also increased in mice exposed to 6 mg/m(3). The amount of collagenous peptides in lavage fluid and total lung collagen were increased in male and female mice exposed to 18 mg/m(3). Acid proteinase activity, principally cathepsin D-like activity, of lung homogenate supernatant fluid was also significantly increased in mice at the 18 mg/m(3) exposure concentration. CONCLUSIONS: Under the conditions of these inhalation studies, there was some evidence of carcinogenic activity of talc in male F344/N rats based on an increased incidence of benign or malignant pheochromocytomas of the adrenal gland. There was clear evidence of carcinogenic activity of talc in female F344/N rats based on increased incidences of alveolar/bronchiolar adenomas and carcinomas of the lung and benign or malignant pheochromocytomas of the adrenal gland. There was no evidence of carcinogenic activity of talc in male or female B6C3F1 mice exposed to 6 or 18 mg/m(3). The principal toxic lesions associated with inhalation exposure to the same concentrations of talc in rats included chronic granulomatous inflammation, alveolar epithelial hyperplasia, squamous metaplasia and squamous cysts, and interstitial fibrosis of the lung. These lesions were accompanied by impaired pulmonary function characterized primarily by reduced lung volumes, reduced dynamic and/or quasistatic lung compliance, reduced gas exchange efficiency, and nonuniform intrapulmonary gas distribution. In mice, inhalation exposure to talc produced chronic inflammation of the lung with the accumulation of alveolar macrophages. Synonyms: talcum; agalite; emtal 596; non-asbestiform talc; non-fibrous talc; steatite; hydrous magnesium silicate

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Triamterene (CAS No. 396-01-0) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Triamterene is a potassium-sparing diuretic used in the treatment of edema associated with congestive heart failure, cirrhosis of the liver, and other diseases in which edema may occur. Toxicity and carcinogenicity studies were conducted by administering triamterene (greater than 99% pure) in feed to groups of male and female F344/N rats and B6C3F1 mice for 15 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Chinese hamster ovary cells. 15-day Studies: Groups of five male and five female rats were fed diets containing 0, 1,000, 3,000, 10,000, 30,000, or 60,000 ppm triamterene. The diets containing 10,000 ppm or more were unpalatable, and feed consumption by the 3,000 ppm groups was reduced. Rats exposed to 1,000 or 3,000 ppm triamterene received approximate doses of 80 or 60 mg/kg body weight per day (males) or 70 or 50 mg/kg per day (females). One male rat and two female rats receiving 3,000 ppm died during the second week of the study. The final mean body weights of 3,000 ppm male and female rats were significantly lower than those of controls. Rats in the 3,000 ppm groups had renal tubule regeneration and cytoplasmic vacuolization of the zona glomerulosa of the adrenal gland. Groups of five male and five female mice were fed diets containing 0, 300, 1,000, 3,000, 10,000, or 30,000 ppm triamterene, but the diets containing 10,000 or 30,000 ppm were unpalatable. All mice receiving 3,000 ppm died by day 6. Mice exposed to 300 or 1,000 ppm triamterene received approximate doses of 40 or 155 mg/kg body weight per day (males) or 45 or 170 mg/kg body weight per day (females). The final mean body weights of mice in the 300 and 1,000 ppm groups were similar to those of the controls. Renal tubule degeneration and necrosis were observed in the kidney of 3,000 ppm mice. 13-Week Studies: Groups of 10 male and 10 female rats were fed diets containing 0, 150, 300, 600, 1,200, or 2,400 ppm triamterene. All rats receiving 2,400 ppm died before the end of the study; all other rats survived to the end of the study. Rats exposed to 150, 300, 600, or 1,200 ppm triamterene received approximate doses of 10, 20, 40, or 70 mg/kg body weight per day (males) or 10, 20, 40, or 80 mg/kg per day (females). Body weight gains and final mean body weights of rats in the 1,200 ppm groups were significantly lower than those of controls. There were no biologically significant differences in hematologic, clinical chemistry, or urinalysis parameters among exposed and control rats. Calculi were observed in the renal pelvis of four male rats in the 1,200 ppm group. Chemical-related lesions were observed in the kidney and adrenal gland of rats in the 1,200 and 2,400 ppm groups. These consisted of degeneration and regeneration of the renal tubule epithelium and cytoplasmic vacuolization of cells of the zona glomerulosa of the adrenal cortex. Depletion of hematopoietic cells from the bone marrow and of lymphocytes from the spleen and thymus of rats in the 2,400 ppm groups may have been related to debilitation and reduced feed consumption rather than chemical exposure. Groups of 10 male and 10 female mice were fed diets containing 0, 100, 200, 400, 800, or 1,600 ppm triamterene. All mice receiving 1,600 ppm, one 800 ppm female, one 200 ppm male, and four 100 ppm males died before the end of the study. Mice exposed to 100, 200, 400, or 800 ppm triamterene received approximate doses of 15, 25, 50, or 90 mg/kg body weight per day (males) or 15, 25, 50, or 115 mg/kg per day (females). The body weight gain and final mean body weight of male mice receiving 800 ppm were significantly lower than those of the controls. The total leukocyte and lymphocyte counts of males receiving 800 ppm and of females receiving 100, 400, or 800 ppm were significantly lower than those of controls. No other differences in hematologic, clinical chemistry, or urinalysis parameters were considered to be biologically significant. Necrosis of Lymphocytes was observed in the lymph node, spleen, and thymus of mice in the 800 and 1,600 ppm groups groups. 2-Year Studies: The doses selected for the 2-year studies were based on lower body weights, mortality, and chemical-related lesions observed in exposed animals during the 13-week studies. Groups of 70 male and 70 female rats were fed diets containing 0, 150, 300, or 600 ppm triamterene and groups of 70 male and 70 female mice were fed diets containing 0, 100, 200, or 400 ppm. Ten animals from each group were included for interim evaluations at 3 and 15 months. Because of a dosing error involving the high-dose mice at week 40, a second study was conducted with groups of 60 male and 60 female mice fed diets containing 0 or 400 ppm triamterene. In the 2-year studies, rats exposed to 150, 300, or 600 ppm triamterene received approximately 5,10, or 25 mg/kg body weight per day (males) and 5, 15, or 30 mg/kg (females) and mice exposed to 100, 200, or 400 ppm received approximately 10, 25, or 45 mg/kg (males) and 15, 30, or 60 mg/kg (females) per day. 3-Month and 15-Month Interim Evaluations in the 2-Year Studies: There were no biologically significant differences in hematologic, clinical chemistry, or urinalysis parameters between exposed and control rats or mice at the 3- or 15-month interim evaluations. At necropsy, the mean body weights of exposed rats and mice were similar to those of the controls. There were no chemical-related lesions in exposed rats at 3 months or in exposed mice at 3 or 15 months. At the 15-month evaluation, basophilic, clear cell, and mixed cell foci of the liver occurred in exposed male rats. No chemical-related lesions were observed in female rats at 15 months. Survival, Body Weights, Clinical Findings, and Feed Consumption in the 2-Year Studies: Survival of exposed rats was similar to that of controls (males: 0 ppm, 25/47; 150 ppm, 25/50; 300 ppm, 19/50; 600 ppm, 27/50; females: 29/50, 34/50, 34/50, 29/50). The mean body weights of 600 ppm rats were consistently lower than, but within 5% of, those of controls after week 49. Feed consumption by male and female rats was similar among exposed and control groups throughout the studies. There were no clinical findings of toxicity. Survival of 400 ppm male mice in the first study was lower than that of controls because of the dosing accident at week 40. Survival of 100 and 200 ppm male mice and of all exposed groups of female mice in the first study and of exposed males and females in the second study was similar to controls (males: first study, 0 ppm, 47/50; 100 ppm, 45/50; 200 ppm, 46/50; 400 ppm, 46/60; second study, 0 ppm, 43/50; 400 ppm, 39/50; females: first study, 38/50; 43/50; 43/50; 43/60; second study, 40/50; 38/51). Mean body weights of exposed mice were similar to those of controls throughout the first study with one exception; in the week following the dosing error, the mean body weight of 400 ppm males was 16% lower than that of controls. In the second study, mean body weights of 400 ppm mice were slightly lower than those of controls during the final 8 weeks. Feed consumption by exposed mice was similar to that by controls throughout the studies. There were no clinical findings of toxicity in exposed mice. Neoplasms and Nonneoplastic Lesions in the 2-Year Studies: The incidences of mixed cell foci and focal hyperplasia of the liver were significantly increased in 300 and 600 ppm male rats, and the incidences of clear cell and mixed cell foci were significantly increased in 300 and 600 ppm female rats. Hepatocellular adenomas occurred in all groups of exposed male rats, but none occurred in controls; the incidence of hepatocellular adenoma in the 150 ppm males was significantly higher than that of controls (O ppm, 0/50; 150 ppm, 6/50; 300 ppm, 4/50; 600 ppm, 3/49). Hepatocellular adenomas were observed in two 600 ppm female rats, but not in the lower exposure groups or in controls. No hepatocellular carcinomas were seen in exposed or control rats. The incidences of nephropathy in exposed rats were similar to those of controls, but the average severity of the lesion was marginally increased in male rats receiving 300 ppm and in female rats receiving 600 ppm (males: 47/50, 2.4; 49/50, 2.7; 50/50, 3.0; 49/50, 2.8; females: 38/50, 1.1; 45/50, 1.2; 45/50, 1.3; 45/50, 1.4). Although in the first study the incidences of hepatocellular adenoma in exposed male mice were similar to that of controls, the incidences of multiple adenomas were greater in the exposed groups, and the incidence of hepatocellular carcinoma in the 400 ppm group was marginally greater (hepatocellular adenoma: 0 ppm, 17/50; 100 ppm, 22/50; 200 ppm, 19/50; 400 ppm, 20/60; hepatocellular carcinoma: 5/50; 7/50; 3/50; 13/60). In the second study, the incidence of hepatocellular adenoma in the 400 ppm males was significantly higher than that of controls (hepatocellular adenoma: 0 ppm, 21/50; 400 ppm, 36/50; hepatocellular carcinoma: 9/50; 11/50). The incidences of hepatocellular adenoma in exposed female mice in the first and second studies were significantly greater than those of controls (hepatocellular adenoma, first study: 10/50; 22/50; 23/50; 36/60; second study: 7/50; 28/51). The incidences of multiple adenoma were also increased in the exposed groups. Although the incidences of hepatocellular carcinoma were similar among exposed and control female mice in the first study, the incidence of hepatocellular carcinoma in the 400 ppm females in the second study was marginally greater than that of controls (hepatocellular carcinoma, first study: 4/50; 4/50; 3/50; 8/60; second study: 5/50; 11/50). In both studies, hepatocellular foci (basophilic, eosinophilic, clear cell, or mixed cell) also occurred more frequently in exposed female mice than in controls. The incidences of thyroid gland follicular cell hyperplasia in the 200 and 400 ppm males and in all exposed groups of females were significantly greater than those of controls in the first study. These findings were confirmed in the second study (follicular cell hyperplasia: males, first study, 3/50, 8/50, 16/50, 20/60; second study, 0/50,16/50; females, first study, 4/49,17/49,18/50, 28/60; second study, 9/50, 32/51). The incidences of follicular cell neoplasms were similar among exposed and control mice in both studies. The incidences (28/50, 36/50, 43/50, 49/60) and average severity (0.56, 0.80, 1.00, 1.07) of nephropathy were marginally higher in exposed female mice than in controls in the first study. In the second study, the differences in incidence (15/50, 21/50) and severity (0.38, 0.55) were not as great. It is uncertain if these increases were related to the ingestion of triamterene. The incidences and severity of nephropathy were similar among exposed and control male mice in both studies. Genetic Toxicology: Triamterene was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 with or without exogenous metabolic activation (S9). It did not induce chromosomal aberrations in Chinese hamster ovary cells, with or without S9. Positive results were obtained for induction of sister chromatid exchanges in Chinese hamster ovary cells with and without S9. Conclusions: Under the conditions of these 2-year feed studies, there was equivocal evidence of carcinogenic activity of triamterene in male F344/N rats based on a marginal increase in the incidence of hepatocellular adenoma. There was no evidence of carcinogenic activity of triamterene in female F344/N rats administered 150, 300, or 600 ppm. There was some evidence of carcinogenic activity of triamterene in male B6C3F1 mice based on a marginal increase in the incidence of hepatocellular carcinoma in the first study and a significantly increased incidence of hepatocellular adenoma in the second study. There was some evidence of carcinogenic activity of triamterene in female B6C3F1 mice based on significantly increased incidences of hepatocellular adenoma and of adenoma and carcinoma (combined). Exposure to triamterene was associated with an increased incidence of hepatocellular foci, primarily mixed cell type, and an increase in the severity of nephropathy in female rats. In mice, exposure to triamterene was associated with an increased incidence of hepatocellular foci in females and an increased incidence of thyroid gland follicular cell hyperplasia in males and females. Synonyms: 6-Phenyl-2,4,7-pteridinetnamine; 6-phenyl-2,4,7-triaminopteridine; 2,4,7-triamino-6-phenypteridine; ademin; pterofen; pterophane; NSC-77625; SKF 8542 Trade names: Dyrenium, Dyazide, Dyren, Dytac, Jatropur, Maxzide, Noridyl, Triteren, Teriam, Urocaudal

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of p-Nitroaniline (CAS No. 100-01-6) in B6C3F1 Mice (Gavage Studies).

p-Nitroaniline is an intermediate in the preparation of several azo dyes used for coloring consumer products. Toxicology and carcinogenicity studies were conducted by administering p-nitroaniline (>99% pure) in corn oil by gavage to groups of male and female B6C3F1 mice for 14 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Chinese hamster ovary cells, mouse Iymphoma cells, and Drosophila melanogaster. 14-DAY STUDIES: Groups of five male and five female B6C3F1 mice received p-nitroaniline in corn oil by gavage at doses of 0, 10, 30, 100, 300, or 1,000 mg/kg body weight 5 days per week for 2 weeks. All mice that received 1,000 mg/kg died from chemical-related toxicity by day 4 of the studies. Final mean body weights of mice receiving 300 mg/kg or less were similar to those of the controls. Hematology results were consistent with chemical-related methemoglobinemia and regenerative anemia. Met hemoglobin concentrations in all groups of dosed mice were significantly higher than those in controls. Hematocrit values in mice that received 300 mg/kg and total erythrocyte counts in mice that received 100 or 300 mg/kg were significantly lower than those in controls. Reticulocyte counts in 300 mg/kg male mice and in 100 or 300 mg/kg females were significantly higher than controls. Heinz bodies were observed in erythrocytes of all 300 mg/kg mice and in two 100 mg/kg male mice. The absolute and relative spleen weights of 100 and 300 mg/kg mice were significantly greater than those of the controls. Hematopoiesis and pigment (hemosiderin) accumulation were observed in the splenic red pulp of males and females receiving 300 mg/kg; pigment (hemosiderin) accumulation in Kupffer cells of the liver was also seen in male mice at this dose level. 13-WEEK STUDIES: Groups of 20 male and 20 female B6C3F1 mice received p-nitroaniline in corn oil by gavage at doses of 0, 1, 3, 10, 30, or 100 mg/kg body weight 5 days per week for up to 13 weeks. Eight or nine mice in each group were evaluated at 7 weeks. There were no deaths associated with exposure to p-nitroaniline, and final mean body weights of dosed mice were similar to those of the controls. Hematologic and pathologic findings at 7 and 13 weeks were similar to those seen in the 14-day studies and occurred primarily in the 30 and 100 mg/kg groups. Met hemoglobin concentrations were increased and hematocrit levels and erythrocyte counts were decreased relative to those of the controls. Heinz bodies were observed in erythrocytes and nucleated erythrocytes and reticulocytes were increased in number. Absolute and relative spleen weights of male and female mice receiving 30 and 100 mg/kg were significantly greater than those of controls at 7 and 13 weeks. Absolute and relative liver weights of female mice necropsied at 7 weeks were significantly greater in the 30 and 100 mg/kg groups; by 13 weeks, both absolute and relative liver weights were similar to control values. The incidence or severity of splenic hematopoiesis and pigmentation (hemosiderin) increased with dose at the 7-week interim evaluations and at the end of the studies. Pigment (hemosiderin) was also present in Kupffer cells of the liver in dosed male mice. 2-YEAR STUDIES: Groups of 70 male and 70 female B6C3F1 mice received p-nitroaniline in corn oil by gavage at doses of 0, 3, 30, or 100 mg/kg body weight for 5 days per week for up to 103 weeks. The dose selection was based on the hematologic and pathologic findings of the 13-week studies. Nine or ten mice from each group were evaluated at 9 and 15 months for the presence of chemical-related lesions. Body Weights, Clinical Findings, Survival, and Hematology: Mean body weights of male and female mice that received p-nitroaniline were similar to those of control mice throughout the 2-year studies. There were no clinical findings associated with chemical exposure, and survival of dosed mice was similar to that of controls. The hematology findings at the 9 and 15-month interim evaluations were similar to those in the 14-day and 13-week s 13-week studies. The methemoglobin concentrations were significantly higher in all 30 or 100 mg/kg mice; sulfhemoglobin concentrations were significantly higher at 9 months in all 30 or 100 mg/kg female mice and at 15 months in 100 mg/kg females. Hematocrit and erythrocyte counts in 100 mg/kg mice were significantly lower than those in controls. By 9 months, reticulocyte counts were significantly higher in all 30 or 100 mg/kg mice. At 15 months, only the 100 mg/kg mice exhibited significantly higher reticulocyte counts. Neoplasms and Nonneoplastic Lesions: Lesions related to the administration of p-nitroaniline occurred in the spleen, liver, and bone marrow, primarily in mice receiving 30 or 100 mg/kg; these were observed at the 9- and 15-month interim evaluations and at the end of the studies. There were increases in the incidence or severity of splenic congestion, hematopoiesis, pigment (hemosiderin) accumulation, Kupffer cell pigmentation in the liver, and bone marrow hypercellularity (hyperplasia). The incidences of hemangiosarcoma of the liver (0 ppm, 0/50; 3 ppm, 1/50; 30 ppm, 2/50; 100 ppm, 4/50) and hemangioma or hemangiosarcoma (combined) at all sites (5/50, 3/50, 4/50, 10/50) were marginally increased in 100 mg/kg male mice. The incidence of hepatocellular adenoma or carcinoma (combined) was significantly decreased (25/50, 26/50, 25/50, 13/50) in 100 mg/kg male mice. GENETIC TOXICOLOGY: p-Nitroaniline is mutagenic in vitro. It was tested in two laboratories for induction of gene mutations in several strains of Salmonella typhimurium. Both studies showed positive results in strain TA98, with and without S9 activation; results were negative for all other strains. p-Nitroaniline was tested in two laboratories for induction of sister cremated exchanges and chromosomal aberrations in Chinese hamster ovary cells. In the sister cremated exchange study, one laboratory reported negative results without S9 and positive results with S9; the second laboratory reported equivocal results without S9 and negative results with S9. In the chromosomal aberrations study, both laboratories found positive results with S9. Without S9, one laboratory reported weakly positive results while the other reported negative results. p-Nitroaniline induced trifluorothymidine resistance in L5178Y mouse Iymphoma cells in the absence of S9; no induction of trifluorothymidine resistance was noted with S9. In contrast to the positive results in the previous tests, p-nitroaniline did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster when administered by feeding or injection to adult males or by feeding to larvae. CONCLUSIONS: Under the conditions of these 2-year gavage studies there was equivocal evidence of carcinogenic activity of p-nitroaniline in male B6C3F1 mice based on the increased incidences of hemangiosarcoma of the liver and hemangioma or hemangiosarcoma (combined) at all sites. There was no evidence of carcinogenic activity of p-nitroaniline in female B6C3F1 mice receiving doses of 3, 30, or 100 mg/kg.

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of p-Nitrophenol (CAS No. 100-02-7) in Swiss Webster Mice (Dermal Studies).

p-Nitrophenol is used in the production of acetaminophen, methyl and ethyl parathion insecticides, fungicides, and dyestuffs. Toxicology and carcinogenesis studies of p-nitrophenol (greater than 97% pure) were conducted by dermal application to male and female Swiss-Webster mice for 18 months. Dermal application was selected as the route of chemical administration because of possible skin absorption from p-nitrophenol-treated leather footwear. Genetic toxicology studies were conducted in Salmonella typhimurium, Chinese hamster ovary cells, and Drosophila melanogaster. 18-MONTH STUDIES: Groups of 60 Swiss-Webster mice of each sex received p-nitrophenol in acetone applied to the interscapular skin. Doses of 0, 40, 80, or 160 mg/kg p-nitrophenol were administered to mice 3 days per week for 78 weeks. At the end of the study, survival rates of mice receiving 0, 40, 80, or 160 mg/kg p-nitrophenol were 29/60, 17/60, 26/60, and 24/60 for males and 35/60, 26/60, 33/60, and 27/60 for females. Deaths after 60 weeks were caused by generalized amyloidosis and secondary kidney failure. The severity of amyloidosis was similar among dosed and control animals. At the end of the study, the final mean body weights of the dosed groups of each sex were similar to those of the controls. No biologically significant lesions were observed that were related to the dermal administration of p-nitrophenol. GENETIC TOXICOLOGY: p-Nitrophenol was not mutagenic in Salmonella typhimurium (strains TA100, TA1535, TA1537, and TA98) with or without exogenous metabolic (S9) activation, or in germ cells of male Drosophila melanogaster administered p-nitrophenol in feed or by injection. In Chinese hamster ovary cells, no induction of sister chromatid exchanges was observed with or without S9, but a significant increase in chromosomal aberrations occurred in trials conducted with S9. CONCLUSIONS: Under the conditions of these 18-month dermal studies there was no evidence of carcinogenic activity in male or female Swiss-Webster mice receiving 40, 80, or 160 mg/kg p-nitrophenol. Synonyms: 4-hydroxynitrobenzene, p-hydroxynitrobenzene, 4-nitrophenol, paranitrophenol, PNP, Niphen

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of o-Nitroanisole (CAS No. 91-23-6) in F344 Rats and B6C3F1 Mice (Feed Studies).

o-Nitroanisole is used as an intermediate for the preparation of o-anisidine and in the manufacture of azo dyes. Toxicology and carcinogenesis studies were conducted by administering o-nitroanisole (>99% pure) in the diet to groups of male and female F344 rats and B6C3F1 mice for 14 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Chinese hamster ovary cells, and mouse lymphoma cells. 14-DAY STUDIES: Groups of five male and five female F344 rats received diets containing 0, 583, 1,166, 2,332, 4,665, or 9,330 ppm o-nitroanisole. Mean body weight gains and final mean body weights of males in the 4,665 and 9,330 ppm groups were lower than those of the controls. Absolute liver weights were significantly increased in males receiving 1,166 ppm or more and in females receiving 583 ppm or more. Groups of five male and five female B6C3F1 mice received diets containing 0, 250, 500, 1,000, 2,000, or 4,000 ppm o-nitroanisole. Mean body weight gains and final mean body weights of males that received 250 ppm and females that received 4,000 ppm were significantly lower than those of the controls. No other chemical-associated effects were observed. 13-WEEK STUDIES: Groups of 10 male and 10 female F344 rats received diets containing 0, 200, 600, 2,000, 6,000, or 18,000 ppm o-nitroanisole. Final mean body weights and feed consumption by male and female rats receiving 6,000 and 18,000 ppm were lower than those of the controls. Hemoglobin and hematocrit values were significantly lower and methemoglobin levels significantly higher in males in the 6,000 and 18,000 ppm groups than in controls. Absolute liver weights were significantly increased in females that received 200, 600, 2,000, and 6,000 ppm, absolute kidney weights were significantly increased in males that received 600, 2,000, and 6,000 ppm, and absolute spleen weights were significantly increased in males and females that received 6,000 and 18,000 ppm. Groups of 10 male and 10 female B6C3F1 mice received diets containing 0, 60, 200, 600, 2,000, or 6,000 ppm o-nitroanisole. Final mean body weight gains, final mean body weights, and feed consumption by male and female mice receiving 6,000 ppm were lower than those of the controls. Hemoglobin and hematocrit values in males and females that received 2,000 or 6,000 ppm were significantly lower than those in the controls. The absolute and relative liver weights of females in the 600 ppm group and relative liver weights of males and females in the 2,000 and 6,000 ppm groups were significantly greater than those of controls. Lesions associated with exposure to o-nitroanisole were present in the urinary bladder, spleen, kidney, liver, testis, and uterus of rats. Diffuse hyperplasia of the transitional epithelium of the urinary bladder occurred in all male and female rats that received 6,000 and 18,000 ppm. A transitional cell papilloma occurred in one male and transitional cell carcinomas occurred in two males and three females receiving 18,000 ppm. Congestion of the red pulp and capsular hyperplasia of the spleen and hepatocellular hypertrophy of the liver were present in males and females from the 18,000 ppm groups. Multifocal degeneration and necrosis of the renal tubule epithelium with infiltration of mononuclear inflammatory cells were present in male rats that received 600, 2,000, and 6,000 ppm. At the 18,000 ppm level, degeneration of the seminiferous epithelium accompanied by loss of spermatogenic cells and decreased numbers of spermatozoa were observed in the testes of male rats, while uterine atrophy was observed in female rats. Hepatocyte hypertrophy of the centrilobular and midzonal regions of liver lobules was present in mice that received 200 ppm and increased in severity at higher exposure levels. 2-YEAR STUDIES: The doses selected for the 2-year study of o-nitroanisole in rats were based on lower mean body weights, reduced feed consumption, and increased severity of regenerative anemia in male and female rats receiving 6,000 and 18,000 ppm during the 13-week study. Groups of 6roups of 60 male and 60 female F344 rats received diets containing 0, 222, 666, or 2,000 ppm o-nitroanisole. Groups of 60 male and 60 female B6C3F1 mice received diets containing 0, 666, 2,000, or 6,000 ppm o-nitroanisole. After 15 months, up to 10 animals from each group were evaluated for chemical-related lesions. Survival, Body Weights, Feed Consumption, and Clinical Findings: Survival of male rats receiving 2,000 ppm was significantly lower than that of the controls due to increased severity of nephropathy. Survival of 222 and 666 ppm male rats and all exposed female rats was similar to that of the controls. Survival of groups of exposed male and female mice was similar to that of the controls. The final mean body weight of male rats receiving 2,000 ppm was lower than that of the controls. Final mean body weights of male and female mice that received 2,000 and 6,000 ppm were lower than those of the controls. Feed consumption by male and female rats was similar to that by the controls. The only clinical finding in male or female mice attributable to chemical administration was discolored urine. Neoplasms and Nonneoplastic Lesions: The incidence of mononuclear cell leukemia was significantly increased in male rats that received 666 and 2,000 ppm and in female rats that received 2,000 ppm (males: 0 ppm, 26/50; 222 ppm, 25/50; 666 ppm, 42/50; 2,000 ppm, 34/50; females: 14/50, 11/50, 14/50, 26/50). Nephropathy occurred in all male rats; the severity increased with exposure level. Focal hyperplasia of the renal tubule epithelium was present in three males receiving 222 ppm and two males receiving 2,000 ppm. Renal tubule adenomas occurred in one male from each of the 222, 666, and 2,000 ppm groups, and renal tubule carcinomas occurred in two males from the 2,000 ppm group. Focal hyperplasia of the transitional epithelium of the urinary bladder was present in one female rat that received 222 ppm and two male rats and six female rats that received 2,000 ppm. A transitional cell papilloma occurred in the urinary bladder of one female rat from the 2,000 ppm group, and a transitional cell carcinoma occurred in another female from the 2,000 ppm group. The incidence of forestomach ulcers increased in male rats that received 2,000 ppm, and the incidence of focal hyperplasia of the forestomach increased with exposure level in male and female rats. In addition, squamous cell papillomas of the forestomach were present in one female receiving 222 ppm, one male receiving 666 ppm, and one male and one female receiving 2,000 ppm, while squamous cell carcinomas were present in one male receiving 666 ppm and one male and one female receiving 2,000 ppm. The incidences of pituitary gland adenomas in male rats and mammary gland fibroadenomas in female rats decreased with exposure level. The incidence of cellular alteration in the liver was significantly increased in exposed groups of male and female mice. The incidences of hepatocellular adenoma, hepatocellular adenoma or carcinoma (combined), and hepatocellular carcinoma or hepatoblastoma (combined) were significantly increased in male mice receiving 2,000 and 6,000 ppm. The incidences of hepatocellular adenoma or carcinoma were significantly increased in female mice that received 2,000 ppm. STOP-EXPOSURE STUDY: Groups of 60 male and 60 female F344 rats received diets containing 0, 6,000, or 18,000 ppm o-nitroanisole for 27 weeks and were then maintained on control feed without further chemical exposure for up to an additional 77 weeks. Up to 10 rats from each group were evaluated for the presence of chemical-related lesions at 3, 6, 9, and 15 months. Survival and Body Weights: Survival of exposed male and female rats was significantly lower than that of the controls as a result of moribund deaths associated with significantly increased incidences of urinary bladder neoplasms, primarily transitional cell carcinomas. All male rats that received 18,000 ppm were dead by week 48 and all females that received 18,000 ppm were dead by week 61. Mean body weights of exposed male and female rats were lower than those of the controls throughout the study. Neoplasms and Nonneoplastic Lesions: Hyperplasia of the transitional epithelium of the urinary bladder was present in nearly all exposed male and female rats examined at the interim evaluations. A transitional cell carcinoma was first observed at the 3-month interim evaluation in a male rat that received 18,000 ppm. At the 6- and 9-month interim evaluations, transitional cell papillomas or carcinomas were observed in both exposed groups of male rats. Transitional cell carcinomas were observed at the 6-month interim evaluation in females receiving 18,000 ppm and at the 9-month interim evaluation in females receiving 6,000 and 18,000 ppm. Adenomatous polyps of the large intestine were observed in a small number of exposed rats at the 6-, 9-, and 15-month interim evaluations. At the end of the study, the incidence of adenomatous polyps of the large intestine was significantly increased in all exposed groups and carcinomas of the large intestine were present in four males and two females from the 18,000 ppm groups. The incidence of hyperplasia of the transitional epithelium of the kidney pelvis was significantly increased in exposed male and female rats and transitional cell papillomas were present in three males and one female that received 18,000 ppm. Transitional cell carcinomas of the kidney were present in one male receiving 6,000 ppm and six males and one female receiving 18,000 ppm. Transitional cell carcinomas of the urinary bladder were seen in nearly all exposed male and female rats. Of the males and females receiving 6,000 ppm which were without carcinomas, three males and one female had transitional cell papillomas. Generalized centrilobular hypertrophy, focal hepatocellular necrosis, multifocal hepatocellular cytoplasmic vacuolation, and Kupffer cell pigmentation were observed in the livers of male and female rats at the 3- and 6-month interim evaluations; however, only Kupffer cell pigmentation was observed at the end of the study. Congestion of the red pulp of the spleen was observed in nearly all exposed male and female rats at the 3-, 6-, and 9-month interim evaluations but the incidence was only slightly increased in the 18,000 ppm groups at the end of the study. Degeneration and atrophy of the seminiferous tubule epithelium of the testes were observed at the 3- and 6-month interim evaluations in all male rats receiving 18,000 ppm. GENETIC TOXICOLOGY: o-Nitroanisole was tested in two laboratories for mutagenicity in Salmonella typhimurium strains TA97, TA98, TA100, TA1535, and TA1537 with and without exogenous metabolic activation (S9). Positive responses were observed at both laboratories in TA100 with and without S9 activation. One laboratory found no increase in mutations, while the second laboratory detected a weakly positive response in TA1535 without S9. No mutagenic activity was observed in the other tester strains. o-Nitroanisole was positive in the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y cells without S9 activation. In cytogenetic tests with Chinese hamster ovary cells, o-nitroanisole induced a significant increase in chromosomal aberrations at the highest dose tested in the presence of S9 activation; sister chromatid exchanges were induced both with and without S9. CONCLUSIONS: Under the conditions of these feed studies there was clear evidence of carcinogenic activity of o-nitroanisole in male and female F344 rats that received diets containing 6,000 or 18,000 ppm for 6 months based on overall increased incidences of benign and malignant neoplasms of the urinary bladder, transitional cell neoplasms of the kidney, and benign and malignant neoplasms of the large intestine. There was a chemical-related increased incidence of mononuclear cell leukemia in male and female rats receiving diets containing 222, 666, or 2,000 ppm o-nitroanisole for 2 years. Marginally increased incidences of uncommon renal tubule neoplasms in male rats and forestomach neoplasms in male and female rats were considered uncertain findings. There was clear evidence of carcinogenic activity of o-nitroanisole in male B6C3F1 mice based on increased incidences of benign and malignant hepatocellular neoplasms. There was some evidence of carcinogenic activity of o-nitroanisole in female B6C3F1 mice based on increased incidences of hepatocellular adenomas. Increased severity of nephropathy in male rats, and increased incidences of focal hyperplasia of the renal tubule epithelium and forestomach ulcers in male rats, and of transitional cell hyperplasia of the urinary bladder, focal hyperplasia of the forestomach, and hyperplasia of transitional epithelium of the kidney pelvis in male and female rats were associated with exposure to o-nitroanisole. Synonyms: Methoxynitrobenzene, nitrophenyl methyl ether

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of 1,3-Butadiene (CAS No. 106-99-0) in B6C3F1 Mice (Inhalation Studies).

1,3-Butadiene is produced in large volumes for use in the manufacture of synthetic rubber and of thermoplastic resins. In previous inhalation studies conducted by the NTP (NTP, 1984) there was clear evidence of multiple organ carcinogenicity in male and female mice exposed to 625 or 1,250 ppm 1,3-butadiene for 60 or 61 weeks. To better characterize exposure-response relationships for neoplasms and nonneoplastic lesions, toxicology and carcinogenesis studies were conducted by exposing groups of male and female B6C3F1 mice to air containing 1,3-butadiene (greater than 99% pure) for up to 2 years. An additional study in male B6C3F1 mice, in which exposure to 1,3-butadiene was stopped after limited exposure periods (13, 26, 40, or 52 weeks), was performed to assess the effects of varying concentration and duration of exposure on the incidences of 1,3-butadiene-induced neoplasms. In vitro genetic toxicology studies were conducted in Salmonella typhimurium and mouse lymphoma cells. In vivo genetic effects were assayed in germ cells of male Drosophila melanogaster and in bone marrow and peripheral blood cells of B6C3F1 mice. 2-Year Studies: Groups of 70 male and 70 female mice were exposed to air containing 0, 6.25, 20, 62.5, or 200 ppm 1,3-butadiene for 6 hours per day, 5 days per week for up to 2 years; groups of 90 male and 90 female mice were exposed to 625 ppm 1,3-butadiene on the same schedule. Up to 10 animals from each group were examined after 9 and 15 months of exposure. Survival and Body Weight in the 2-Year Studies: Two-year survival was decreased for males and females exposed to concentrations of 20 ppm or above, primarily due to the development of chemical-related malignant neoplasms. No female mice exposed to 200 or 625 ppm or males exposed to 625 ppm survived to the end of the studies (males: 35/50, 39/50, 24/50, 22/50, 4/50, 0/70; females: 37/50, 33/50, 24/50, 11/50, 0/50, 0/70). Mean body weights of exposed male and female mice were similar to those of the controls. Hematologic Effects in the 2-Year Studies: Hematologic parameters were evaluated after 9 and 15 months of exposure. At 9 months, decreases in erythrocyte counts, hemoglobin concentration, and packed red cell volume were observed in male mice exposed to 62.5 ppm or above and in female mice exposed to 200 or 625 ppm. Mean erythrocyte volume was increased in male mice exposed to 625 ppm and in females exposed to 200 or 625 ppm. At 15 months, decreases in erythrocyte counts, hemoglobin concentration, and packed red cell volume and increases in mean erythrocyte volume were observed in male and female mice exposed to 625 ppm. Neoplasms and Nonneoplastic Lesions in the 2-Year Studies: Exposure of mice to 1,3-butadiene induced benign and malignant neoplasms at multiple sites. Statistically significant increases in the incidences of neoplasms at one or more sites were seen at concentrations of 20 ppm and higher in males and 6.25 ppm and higher in females. There was no exposure level in this study at which a significant carcinogenic response was not observed. Statistically significant increases occurred in the incidences of malignant lymphoma; histiocytic sarcoma; cardiac hemangiosarcoma; harderian gland adenoma; hepatocellular adenoma and carcinoma; alveolar/bronchiolar adenoma and carcinoma; mammary gland carcinoma, adenoacanthoma, and malignant mixed tumor (females only); benign and malignant ovarian granulosa cell tumor; and forestomach squamous cell papilloma and carcinoma. Low incidences of uncommon neoplasms also occurred in exposed male and female mice, including intestinal carcinomas in males, renal tubule adenomas in males and females, skin sarcomas (all types combined) in females, and Zymbal's gland adenomas and carcinomas in females. Lymphocytic lymphomas appeared as early as week 23 and were the principal cause of death of male and female mice exposed to 625 ppm 1,3-butadiene. The early and extensive development of lethal lymphocytic lymphomas in mice exposed to 625 ppm resulted in a reduced number of mice at risk for neoplasms developing laterg later at other sites. Exposure-response relationships for 1,3-butadiene-induced neoplasms were more clearly characterized at concentrations below 625 ppm and after adjustment for intercurrent mortality. Increased incidences of nonneoplastic lesions in exposed mice included bone marrow atrophy; testicular atrophy; ovarian atrophy, angiectasis, germinal epithelial hyperplasia, and granulosa cell hyperplasia; uterine atrophy; cardiac endothelial hyperplasia and mineralization; alveolar epithelial hyperplasia; forestomach epithelial hyperplasia; and harderian gland hyperplasia. Stop-Exposure Study: The stop-exposure study consisted of groups of 50 male mice exposed to 1,3-butadiene at concentrations of 200 ppm for 40 weeks, 625 ppm for 13 weeks, 312 ppm for 52 weeks, or 625 ppm for 26 weeks. After the exposures were completed, these groups were placed in control chambers for the remainder of the 2-year study. The total exposure of 1,3-butadiene (concentration times duration of exposure) of the 13- and 40-week stop-exposure groups was approximately 8,000 ppm-weeks, while that of the 26- and 52-week stop-exposure groups was approximately 16,000 ppm-weeks. The survival of all stop-exposure groups was markedly lower than that of the controls. The incidences of lymphocytic lymphoma, histiocytic sarcoma, cardiac hemangiosarcoma, alveolar/bronchiolar adenoma and carcinoma, forestomach squamous cell papilloma and carcinoma, hepatocellular adenoma, harderian gland adenoma and adenocarcinoma, and preputial gland carcinoma were significantly increased. Neoplasms were induced at most of these sites after only 13 weeks of exposure to 1,3-butadiene. Additionally, low numbers of malignant gliomas and neuroblastomas of the brain and Zymbal's gland carcinomas occurred in one or more stop-exposure groups. At similar total exposures, the incidence of lymphocytic lymphoma was greater with exposure to a higher concentration of 1,3-butadiene for a short time compared with exposure to a lower concentration for an extended period (34% at 625 ppm for 13 weeks versus 12% at 200 ppm for 40 weeks; 60% at 625 ppm for 26 weeks versus 8% at 312 ppm for 52 weeks). Genetic Toxicology: 1,3-Butadiene has been tested both in vitro and in vivo for mutagenic activity. In vitro, positive results were obtained in the Salmonella typhimurium gene mutation assay with strain TA1535; mutagenic activity was not observed in other S. typhimurium strains (TA100, TA97, and TA98). 1,3-Butadiene was negative in the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y cells with and without S9. In vivo, 1,3-butadiene did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster; however, it did induce significant increases in chromosomal aberrations and sister chromatid exchanges in bone marrow cells of mice exposed for 2 weeks by inhalation. In addition, significant increases in micronucleated erythrocytes were observed in peripheral blood samples obtained from male and female mice exposed to 1,3-butadiene for 2 or 13 weeks or 15 months by inhalation. Conclusions: The previous inhalation studies of 1,3-butadiene (TR-288) in male and female B6C3F1 mice provided clear evidence of carcinogenicity at exposure concentrations of 625 or 1,250 ppm. The present inhalation studies - 2-year exposures of 6.25, 20, 62.5, 200, or 625 ppm or shorter duration exposures of 200, 312, or 625 ppm - provide a better characterization of the concentration-dependent responses for 1,3-butadiene-induced neoplasms and nonneoplastic lesions. The present studies confirmed the clear evidence of carcinogenicity of 1,3-butadiene in male B6C3F1 mice based on increased incidences of neoplasms in the hematopoietic system, heart, lung, forestomach, liver, harderian gland, preputial gland, brain, and kidney. There was clear evidence of carcinogenicity of 1,3-butadiene in female B6C3F1 mice based on increased incidences of neoplasms in the hematopoietic system, heart, lung, forestomach, liver, harderian gland, ovary, and mammary gland. Low incidences of intestinal carcinomas in male mice, Zymbal's gland carcinomas in male and female mice, and renal tubule adenomas and skin sarcomas in female mice may also have been related to administration of 1,3-butadiene. Synonyms: alpha,gamma-Butadiene; bivinyl; divinyl; erythrene; vinylethylene; biethylene; pyrrolylene

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Benzyl Acetate (CAS No. 140-11-4) in F344/N Rats and B6C3F1 Mice Feed Studies).

Benzyl acetate is used as a flavoring agent in foods, as a fragrance in soaps and perfumes, as a solvent for cellulose acetate and nitrate, and as a component of printing inks and varnish removers. The NTP previously studied the toxicology and carcinogenicity of this chemical in F344/N rats and B6C3F1 mice using the gavage route of administration and corn oil as a vehicle. Benzyl acetate increased the incidences of pancreatic acinar cell adenomas in male rats and the incidences of hepatocellular adenomas and forestomach neoplasms in male and female mice. Because of the confounding effect of corn oil on the incidences of pancreatic neoplasms and because of controversy over the use of the gavage route of administration, the NTP decided to restudy benzyl acetate using the dosed feed route of administration. In these repeat studies, male and female F344/N rats and B6C3F1 mice received benzyl acetate (at least 98% pure) in feed for 13 weeks and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium nunnery, cultured Chinese hamster ovary cells, LS178Y mouse lymphoma cells, Drosophila melanogaster, and mouse bone marrow and peripheral blood cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 0, 3,130, 6,250,12,500, 25,000, or 50,000 ppm (0, 230, 460, 900,1,750, or 3,900 mg/kg body weight for males and 0, 240, 480, 930,1,870, or 4,500 mg/kg for females) benzyl acetate for 13 weeks. Nine male and nine female rats receiving 50,000 ppm benzyl acetate died or were killed moribund between weeks 2 and 8 of the study. The mean body weight gain and the final mean body weight of 25,000 ppm males were significantly lower (P</=0.01) than those of the control group. Feed consumption by exposed rats, except the 25,000 and S0,000 ppm males and 50,000 ppm females, was similar to that by the controls. The reduced feed consumption by 25,000 and 50,000 ppm males and 50,000 ppm females may have been due to toxicity or decreased palatability. Tremors and ataxia occurred only in the 50,000 ppm rats. These findings were first observed on day 15 in nine males and six females and continued until the end of the study. Cholesterol levels in 12,500 and 25,000 ppm females and triglyceride levels in 25,000 ppm females were lower than those in the controls. Chemical-related lesions occurred in the brain, kidney, tongue, and skeletal muscles of the thigh. Necrosis of the brain involving the cerebellum and/or hippocampus, degeneration and regeneration of the renal tubule epithelium, and degeneration and sarcolemma nuclear hyperplasia of the tongue and skeletal muscles occurred in most male and female 50,000 ppm rats. This effect was observed in the 1,000 mg/kg group in the previous gavage study (NTP, 1986). 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 0, 3, 130, 6,250, 12,500, 25,000, or 50,000 ppm (0, 425, 1,000, 2,000, 3,700, or 7,900 mg/kg body weight for males and 0, 650, 1,280, 2,980, 4,300, or 9,400 mg/kg for females) benzyl acetate. One 50,000 ppm male mouse died and one 50,000 ppm female mouse was killed moribund before the end of the study. Mean body weight gains and final mean body weights of all exposed male and female mice were significantly lower than those of the controls and the mean body weight gains decreased with increased exposure level. Feed consumption by 3,130 ppm males and all exposed females was lower than that by the controls. Tremors occurred only in females and were first observed on day 16 in three females receiving 50,000 ppm, day 94 in one female receiving 25,000 ppm, and day 93 in one female receiving 12,500 ppm. The tremors continued until the end of the study. Necrosis of the brain involving the hippocampus occurred in four 50,000 ppm mice, one male and three females. Hepatocellular necrosis also occurred in the male with brain lesions. On reexamination of the previous 13-week gavage study (NTP, 1986), a similar lesion was seen in the brain of one 1,000 mg/kg female mouse; none were seen in 1,000 mg/kg male mi male mice. The lesion was less severe than that described in the present dosed feed study. The highest dose used in the gavage study was 1,000 mg/kg compared to an estimated high dose of 7,200 mg/kg for the feed study. 2-YEAR STUDY IN RATS: The doses selected for the 2-year feed study of benzyl acetate in F344/N rats were based on lower survival, mean body weights, and feed consumption, and on increased incidences of histopathologic brain lesions in 50,000 ppm male and female rats in the 13-week study. Groups of 60 male and 60 female F344/N rats were fed diets containing 0, 3,000, 6,000, or 12,000 ppm benzyl acetate for 2 years. Survival, Body Weights, Feed and Compound Consumption, and Clinical Pathology: Survival of exposed rats was similar to that of the controls. The mean body weights of the 12,000 ppm males and exposed females were approximately 5&percnt; lower than those of the controls throughout most of the study. The feed consumption by 12,000 ppm males was slightly lower than that by the controls. Dietary levels of 3,000, 6,000, and 12,000 ppm benzyl acetate were estimated to result in average daily consumption levels of 130, 260, and 510 mg/kg body weight (males) and 145, 290, and 575 mg/kg (females). No biologically significant changes in hematology or clinical chemistry parameters were found that could be attributed to benzyl acetate administration. Pathology Findings: No compound-related increased incidences of neoplasms or nonneoplastic lesions occurred in male or female F344/N rats receiving benzyl acetate for as long as 2 years. 2-YEAR STUDY IN MICE: The doses selected for the 2-year feed study of benzyl acetate in B6C3F1 mice were based primarily on lower body weight gains and lower final mean body weights of exposed mice in the 13-week study. Groups of 60 male and 60 female B6C3F1 mice were fed diets containing 0, 330, 1,000, or 3,000 ppm benzyl acetate for 2 years. Survival, Body Weights, Feed and Compound Consumption, and Clinical Pathology: Survival of all exposed mice, except the 3,000 ppm females, was similar to that of the control groups. Survival of 3,000 ppm females was significantly higher than that of the control group. Throughout the 2-year study, the mean body weights of 1,000 and 3,000 ppm males and females were 2&percnt; to 14&percnt; lower than those of the control groups. Dietary levels of 330, 1,000, and 3,000 ppm benzyl acetate were estimated to result in average daily consumption levels of 35, 110, and 345 mg/kg (males) and 40, 130, and 375 mg/kg (females). No biologically significant changes in hematology or clinical chemistry parameters were observed in mice receiving 330,1,000, or 3,000 ppm benzyl acetate. Pathology Findings: No increase in neoplasm incidence in mice could be attributed to benzyl acetate administration in feed. This contrasts with the previous finding that administration of benzyl acetate in corn oil by gavage once daily 5 days a week for as long as 2 years was carcinogenic to mice, causing increased incidences of hepatocellular neoplasms and forestomach neoplasms. The contrast in results between the two studies may be due to differences in the dose levels used (highest dose: gavage, 1,000 mg/kg a day; feed, 360 mg/kg a day). Dose-related increased incidences or severities of nonneoplastic nasal lesions occurred in the most posterior portions of the nasal cavity in all exposed groups. The lesions occurred in the majority of the exposed mice and consisted of atrophy and degeneration, primarily of the olfactory epithelium, cystic hyperplasia of the nasal submucosal glands, pigmentation of the mucosal epithelium, and exudate accumulation. GENETIC TOXICOLOGY: Benzyl acetate was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, with or without exogenous metabolic activation (S9). However, a positive response was observed for benzyl acetate, with and without S9, in the mouse lymphoma assay for induction of trifluorothymidine resistance in L5178Y cells. No significant increases in the frequencies of sister chromatid exchanges or chromosomal aberrations occurred in cultured Chinese hamster ovary cells treated with benzyl acetate in vitro, with or without S9, and no increases in either sister chromatid exchanges or chromosomal aberrations occurred in bone marrow cells of male mice treated in vivo by intraperitoneal injection. No increase in sex-linked recessive lethal germ cell mutations occurred in male Drosophila melanogaster administered benzyl acetate in feed or by injection. Tests of benzyl acetate for induction of micronucleated erythrocytes in bone marrow and peripheral blood of mice were also negative. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of benzyl acetate in male or female F344/N rats receiving 3,000, 6,000, or 12,000 ppm; however, rats may have tolerated higher doses. There was no evidence of carcinogenic activity of benzyl acetate in male or female B6C3F1 mice receiving 330, 1,000, or 3,000 ppm. Nasal lesions associated with benzyl acetate exposure in male and female mice included nasal mucosa atrophy and degeneration (primarily of the olfactory epithelium), cystic hyperplasia of the nasal submucosal gland, and luminal exudate and pigmentation of the nasal mucosal epithelium. In previous 2-year gavage studies (TR-250), benzyl acetate increased the incidence of acinar cell adenomas of the exocrine pancreas in male F344/N rats; the gavage vehicle may have been a contributing factor. There was no evidence of carcinogenic activity in female F344/N rats receiving 250 or 500 mg/kg a day. There was some evidence of carcinogenic activity in male and female B6C3F1 mice, indicated by the increased incidences of hepatocellular adenomas and squamous cell neoplasms of the forestomach. Synonyms: acetic acid benzyl ester, acetic acid phenyl methyl ester, (acetoxymethyl)benzene, acetoxytoluene, benzyl ethanoate, phenylmethyl acetate

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Manganese (II) Sulfate Monohydrate (CAS No. 10034-96-5) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Manganese is the 12th most abundant element in the earth's crust. The base metal does not occur naturally, but is a component of more than 100 minerals, including sulfides, oxides, carbonates, silicates, phosphates, and borates. In addition to occurring in foods and drinking water, manganese occurs in the atmosphere from dust, volcanic activity, forest fires, and industrial emissions. Manganese (II) sulfate monohydrate was chosen for study because of its stability, solubility, and availability. Toxicology and carcinogenesis studies were conducted by administering manganese (II) sulfate monohydrate (97% pure) in feed to groups of male and female F344/N rats and B6C3F1 mice for 14 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, germ cells of Drosophila melanogaster, and cultured Chinese hamster ovary cells. 14-DAY STUDY IN RATS: Groups of five male and five female rats received diets containing 0, 3,130, 6,250, 12,500, 25,000, or 50,000 ppm manganese (II) sulfate monohydrate. All rats survived to the end of the study. Male rats exposed to 50,000 ppm had a mean body weight gain 57% lower and a final mean body weight 13% lower than those of the controls. The mean body weight gain of 50,000 ppm females was 20% lower and the final mean body weight was 7% lower than those of the controls. During the second week, 50,000 ppm males and females exhibited diarrhea. 14-DAY STUDY IN MICE: Groups of five male and five female mice received diets containing 0, 3,130, 6,250, 12,500, 25,000, or 50,000 ppm manganese (II) sulfate monohydrate. One female mouse in the 25,000 ppm group died on day 1 of unknown causes; all other mice survived to the end of the study. Differences in body weights between exposed and control mice could not be attributed to chemical administration. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats received diets containing 0, 1,600, 3,130, 6,250, 12,500, or 25,000 ppm manganese (II) sulfate monohydrate. Mean daily ingestion of manganese (II) sulfate monohydrate ranged from 110 to 1,700 mg/kg body weight in males and 115 to 2,000 mg/kg in females. All rats survived to the end of the study. Mean body weight gains were marginally lower than that of controls in males exposed to 3,130 ppm or more; mean body weight gains were significantly lower than that of the controls in females exposed to 6,250,12,500, or 25,000 ppm. At the end of the study, absolute and relative liver weights of all exposed male rats and of 25,000 ppm female rats were significantly lower than those of controls. The total leukocyte count in males was similar between exposed and control rats; however, neutrophil counts of all exposed groups were greater than those of the controls, whereas lymphocyte counts of the 6,250, 12,500, and 25,000 ppm groups were significantly lower than those of the controls. Total leukocyte counts in 6,250,12,500, and 25,000 ppm females were significantly decreased because of a decrease in lymphocytes. Male rats also demonstrated marginal but significant increases in percent hematocrit and erythrocyte count in the 6,250,12,500, and 25,000 ppm groups. No clinical or histopathologic findings in rats were chemical related. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice received diets containing 0, 3,130, 6,250, 12,500, 25,000, or 50,000 ppm manganese (II) sulfate monohydrate. Mean daily ingestion of manganese (II) sulfate monohydrate ranged from 330 to 7,400 mg/kg body weight in males and 390 to 6,900 mg/kg body weight in females. No deaths were chemical related. The mean body weight gains of exposed male mice and of 50,000 ppm female mice were significantly lower than those of controls. The absolute and relative liver weights of 50,000 ppm males were significantly lower than those of controls. The percent hematocrit and hemoglobin concentration of males and females exposed to 50,000 ppm were lower than those of the controls, and the mean erythrocyte volumes were significantly lower than those of the controls. The total leukocyte counts of males in the 25,eukocyte counts of males in the 25,000 and 50,000 ppm groups were significantly lower than that of the controls. No clinical findings were attributed to manganese (II) sulfate monohydrate ingestion. Epithelial hyperplasia and hyperkeratosis of the forestomach occurred in three 50,000 ppm males. 2-YEAR STUDY IN RATS: Groups of 70 male and 70 female rats were fed diets containing 0, 1,500, 5,000, or 15,000 ppm manganese (II) sulfate monohydrate. Based on average daily feed consumption, these doses resulted in the daily ingestion of 60, 200, or 615 mg/kg body weight (males) or 70, 230, or 715 mg/kg (females). Eight to 10 rats from each group were evaluated at 9 and 15 months. Survival, Body Weights, Feed Consumption, and Clinical Findings: Survival of 15,000 ppm male rats in the 2-year study was significantly lower than that of the control group. The deaths of males in the control and exposure groups were attributed to a variety of spontaneous neoplastic and nonneoplastic lesions; however, the greater number of deaths in the 15,000 ppm group resulted from increased incidences of advanced renal disease related to ingestion of manganese (II) sulfate monohydrate. The decreased survival of the 15,000 ppm males did not occur until approximately week 93 of the study; before week 93, survival was similar in all groups. Survival of exposed females was similar to that of the controls. The mean body weight of 15,000 ppm male rats was within 5&percnt; of the control group until week 89, by week 104, the mean body weight of 15,000 ppm males was 10&percnt; lower than that of the control group. The mean body weights of 1,500 and 5,000 ppm male rats and all exposed female groups were similar to those of the controls throughout the study. Feed consumption by all exposure groups was similar to that by the control groups. No clinical findings were attributed to manganese (II) sulfate monohydrate ingestion. Hematology, Clinical Chemistry, and Tissue Metal Concentration Analyses No differences in hematology and clinical chemistry parameters attributable to the ingestion of manganese (II) sulfate monohydrate occurred between exposed and control groups. At both the 9- and 15-month interim evaluations, tissue concentrations of manganese were significantly elevated in the livers of 5,000 and 15,000 ppm male and female rats, with an accompanying depression of hepatic iron. Pathology Findings: The ingestion of diets containing 15,000 ppm manganese (II) sulfate monohydrate was associated with a marginal increase in the average severity of nephropathy in male rats (0 ppm, 2.9; 1,500 ppm, 3.0; 5,000 ppm, 3.0; 15,000 ppm, 3.2). The increased severity of nephropathy in the 15,000 ppm male rats was accompanied by significantly increased incidences of mineralization of the blood vessels (4/52, 10/51, 6/51,17/52) and glandular stomach (8/52,13/51, 9/51, 23/52), parathyroid gland hyperplasia (14/51, 14/46, 12/49, 23/50), and fibrous osteodystrophy of the femur (12/52,14/51,12/51, 24/52). These lesions are manifestations of renal failure, uremia, and secondary hyperparathyroidism. The increased incidence of advanced renal disease caused reduced survival of the high-dose male rats. No increase in the incidence of neoplasms in male or female rats was attributed to the ingestion of diets containing manganese (II) sulfate monohydrate. 2-YEAR STUDY IN MICE: Groups of 70 male and 70 female mice received diets containing 0, 1,500, 5,000, or 15,000 ppm manganese (II) sulfate monohydrate. These levels resulted in an average daily ingestion of 160, 540, or 1,800 mg/kg body weight (males) or 200, 700, or 2,250 mg/kg (females). Nine or 10 mice from each group were evaluated at the 9-month and 15-month interim evaluations. Survival, Body Weights, Feed Consumption, and Clinical Findings: Survival rates of exposed male and female mice in the 2-year study were similar to those of the control groups. The mean body weights of exposed male mice were similar to that of the control group. Compared to controls, female mice had exposure related lower mean body weights after week 37, and the final mean body weights for the 1,500, 5,000, and 15,000 ppm groups were 6&percnt;, 9&percnt;, and 13&percnt; lower than that of the control group. Feed consumption by all exposure groups was similar to that by the control groups. No clinical findings were attributed to the administration of manganese (II) sulfate monohydrate. Hematology, Clinical Chemistry, and Tissue Metal Concentration Analyses No chemical-related differences between exposed and control groups occurred in hematology or clinical chemistry parameters. At the 9- and 15-month interim evaluations, tissue concentrations of manganese were significantly elevated in the livers of the 5,000 and 15,000 ppm groups. Hepatic iron levels were significantly lower in exposed females at the 9-month interim evaluation and in 5,000 and 15,000 males and all exposed females at the 15-month interim evaluation. Pathology Findings: Incidences of thyroid follicular dilatation and hyperplasia were significantly greater in 15,000 ppm male and female mice than in controls. Follicular cell adenomas occurred in one 15,000 ppm male at the 15-month interim evaluation and in three 15,000 ppm males at the end of the study but not in the lower exposure groups or the control group. Follicular cell adenomas also occurred in two control, one 1,500, and five 15,000 ppm female mice at the end of the study. It is uncertain if the slightly increased incidence of follicular cell adenoma is related to the ingestion of manganese (II) sulfate monohydrate. The incidences of focal hyperplasia of the forestomach epithelium were significantly greater in the 15,000 ppm male and exposed female groups. The hyperplasia was associated with ulcers and inflammation in some mice, particularly males. GENETIC TOXICOLOGY: Manganese (II) sulfate monohydrate was not mutagenic in Salmonella typhimurium strains TA97, TA98, TA100, TA1535, or TA1537, with or without exogenous metabolic activation (S9), and did not induce sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster. Tests for induction of sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells treated without S9 were positive; with S9, only the sister chromatid exchange test with manganese (11) sulfate monohydrate was positive. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of manganese (II) sulfate monohydrate in male or female F344/N rats receiving 1,500, 5,000, or 15,000 ppm. There was equivocal evidence of carcinogenic activity of manganese (II) sulfate monohydrate in male and female B6C3F1 mice, based on the marginally increased incidences of thyroid gland follicular cell adenoma and the significantly increased incidences of follicular cell hyperplasia. The ingestion of diets containing manganese (II) sulfate monohydrate was associated with an increased severity of nephropathy in male rats, focal squamous hyperplasia of the forestomach in male and female mice, and ulcers and inflammation of the forestomach in male mice. These studies were not designed to assess any neurotoxicity that might have been expected with chronic exposure to sufficiently high doses of manganese. Synonyms: Manganese sulfate; manganous sulfate; sulfuric acid. manganese2+ salt (1:1), monohydrate

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Turmeric Oleoresin (CAS No. 8024-37-1) (Major Component 79%-85% Curcumin, CAS No. 458-37-7) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Turmeric oleoresin is the organic extract of turmeric, a ground powder from the root of the Curcuma plant, and is added to food items as a spice and coloring agent. Turmeric oleoresin, turmeric, and curcumin (the major component found in turmeric) were nominated by the National Cancer Institute and the Food and Drug Administration for study because these chemicals are used in food items and curry powders, and there was little information on their toxic or carcinogenic properties. Pure curcumin was not available in sufficient quantities for study, and a turmeric oleoresin with a high curcumin content (79% to 85%) was selected for evaluation. Toxicity and carcinogenicity studies were conducted by administering turmeric oleoresin in feed to groups of male and female F344/N rats and B6C3F1 mice for 13 weeks and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 0, 1,000, 5,000, 10,000, 25,000, or 50,000 ppm turmeric oleoresin. All rats survived until the end of the study. The final mean body weight of males receiving 50,000 ppm was 5% lower than that of the controls. Feed consumption by exposed male and female rats was similar to that by the controls. Dietary levels of 1,000, 5,000,10,000, 25,000, or 50,000 ppm turmeric oleoresin were estimated to deliver average daily doses of 50, 250, 480, 1,300, or 2,600 mg/kg body weight to males and 60, 300, 550, 1,450, or 2,800 mg/kg to females. The absolute and relative liver weights of female rats and the relative liver weights of male rats receiving 5,000, 10,000, 25,000, and 50,000 ppm were significantly greater than those of the controls. There were no biologically significant differences in hematologic, clinical chemistry, or urinalysis parameters. Clinical findings included stained fur, and discolored feces and urine of exposed animals, presumably due to the parent compound or its metabolites. Hyperplasia of the mucosal epithelium was observed in the cecum and colon of male and female rats that received 50,000 ppm. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 0,1,000, 5,000,10,000, 25,000, or 50,000 ppm turmeric oleoresin. There were no deaths attributed to turmeric oleoresin and the final mean body weight gains and final mean body weights of all exposed groups of male and female mice were similar to those of the controls. Feed consumption by exposed male and female mice was similar to that by the controls. Dietary levels of 1,000, 5,000,10,000, 25,000, or 50,000 ppm turmeric oleoresin were estimated to deliver average daily doses of 150, 750, 1,700, 3,850, or 7,700 mg/kg body weight to males and 200, 1,000, 1,800, 4,700 or 9,300 mg/kg to females. Absolute and relative liver weights of male mice that received 5,000 ppm and male and female mice that received 10,000, 25,000 and 50,000 ppm were significantly greater than those of the controls. Clinical findings in mice included stained fur, and discolored feces and urine. There were no biologically significant differences in hematologic, clinical chemistry, or urinalysis parameters, and there were no chemical related histopathologic lesions. 2-YEAR STUDY IN RATS: The exposure level selection for the 2-year study was based on the 13-week study, which showed that rats could tolerate diets containing up to 50,000 ppm. Groups of 60 male and 60 female F344/N rats were fed diets containing 2,000, 10,000, or 50,000 ppm turmeric oleoresin for 104 (males) or 103 (females) weeks, which were estimated to deliver average daily doses of 80, 460, or 2,000 mg/kg to males and 90, 440, or 2,400 mg/kg to females. Nine or 10 rats from each exposure group were evaluated after 15 months. Survival, Mean Body Weights, Feed Consumption, and Clinical Findings: Survival of exposed male and female rats was similar to that of the controls (male: O ppm, 18/50; 2,000 ppm, 17/50; 10,000 ppm, 15/50; 50,000 ppm, 17/50; female: 33/50, 27/50, 28/50, 34/50). Th50, 28/50, 34/50). The final mean body weights of all exposed male rats and female rats receiving 2,000 and 10,000 ppm were similar to those of the controls. The final mean body weights of male and female rats that received 50,000 ppm were slightly lower (up to 10&percnt;) than those of the controls throughout much of the study. Feed consumption by exposed male and female rats was similar to that by controls throughout the study. The absolute and relative liver weights of female rats receiving 10,000 or 50,000 ppm were significantly greater than those of controls at the 15-month interim evaluation. There were no clinical findings related to toxicity. Hematology and Clinical Chemistry: In male and female rats receiving 50,000 ppm the hematocrit values, hemoglobin concentrations, and erythrocyte counts at the 15-month interim evaluation were significantly lower than those in the controls. In addition, platelet counts in male and female rats that received 50,000 ppm and reticulocyte counts in male rats that received 50,000 ppm were significantly higher than those in the controls. No biologically significant differences were observed in clinical chemistry parameters. Pathology Findings: Chemical-related nonneoplastic lesions occurred in the gastrointestinal tract of rats that received 50,000 ppm. Males receiving 50,000 ppm had increased incidences of ulcers, hyperplasia, and hyperkeratosis of the forestomach. Male and female rats that received 50,000 ppm had ulcers, chronic active inflammation, and hyperplasia of the cecum. Similar lesions also occurred in the colon of males receiving 50,000 ppm. Male and female rats that received 50,000 ppm and male rats that received 10,000 ppm had significantly increased incidences of sinus ectasia of the mesenteric Iymph node. The incidences of clitoral gland adenoma in all exposed groups of female rats were significantly increased. Clitoral gland carcinomas occurred in one control female and in four 2,000 ppm females, but not in females that received 10,000 or 50,000 ppm. The incidences of clitoral gland adenoma or carcinoma (combined) in all exposed groups of female rats were similar (6/50, 16/48, 15/47, 16/49) and did not increase with exposure level. The incidence of clitoral gland hyperplasia was similar among exposed and control groups of female rats (7/50, 5/48, 4/47, 7149). 2-YEAR STUDY IN MICE: The exposure level selection for the 2-year study was based on the 13-week study, which showed that mice could tolerate diets containing up to 50,000 ppm. Groups of 60 male and 60 female B6C3F1 mice were fed diets containing 2,000, 10,000, or 50,000 ppm turmeric oleoresin for 103 weeks, which were estimated to deliver average daily doses of 220, 520, or 6,000 mg/kg to males and 320,1,620, or 8,400 mg/kg to females. Nine or 10 mice from each exposure group were evaluated after 15 months. Survival, Mean Body Weights, Feed Consumption, and Clinical Findings: Survival of exposed male and female mice was similar to that of the controls (male: O ppm, 43/50; 2,000 ppm, 43/50; 10,000 ppm, 37/50; 50,000 ppm 42/50; female: 39/50, 41/50, 34/50, 42/50). The mean body weight of female mice receiving 50,000 ppm was slightly lower (up to 12&percnt;) than that of the controls from about week 25. The final mean body weights of males that received 50,000 ppm and females that received 10,000 and 50,000 ppm were significantly lower than those of controls. The final mean body weights of other exposed groups of male and female mice were similar to those of the controls. Feed consumption by exposed male and female mice was similar to that by the controls throughout the study. The absolute and relative liver weights of male and female mice receiving 10,000 and 50,000 ppm were significantly greater than those of the controls at the l5-month interim evaluation. There were no clinical findings related to toxicity. Hematology and Clinical Chemistry: No biologically significant differences were observed in hematologic parameters. The alkaline phosphatase values of male and female mice that received 10,000 and 50,000 ppm were significantly higher than those of controls at the 15-month interim evaluation. Pathology Findings: The incidences of hepatocellular adenoma in male and female mice receiving 10,000 ppm, but not those in mice receiving 2,000 or 50,000 ppm, were significantly increased (male: 25/50, 28/50, 35/50, 30/50; female: 7/50, 8/50, 19/51, 14/50). The number of male and female mice in the 10,000 and 50,000 ppm groups with multiple hepatocellular neoplasms was significantly greater than that in the controls. The incidences of hepatocellular carcinoma were similar among exposed and control groups. In contrast to rats, there were no chemical-related nonneoplastic lesions of the gastrointestinal tract in mice. Three males that received 2,000 ppm and three males that received 10,000 ppm had carcinomas of the small intestine; neoplasms of the small intestine were not observed in control males or in males that received 50,000 ppm. Female mice receiving 50,000 ppm had a significantly increased incidence of thyroid gland follicular cell hyperplasia. GENETIC TOXICOLOGY: Turmeric oleoresin was not mutagenic in Salmonella typhimurium strains TA100, TA1535, TA1537, or TA98 with or without exogenous metabolic activation (S9). It induced small but significant increases in sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells. The positive response in the sister chromatid exchange test occurred in the presence of S9, whereas the aberrations response occurred without S9. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of turmeric oleoresin in male F344/N rats administered 2,000, 10,000, or 50,000 ppm. There was equivocal evidence of carcinogenic activity of turmeric oleoresin in female F344/N rats based on increased incidences of clitoral gland adenomas in the exposed groups. There was equivocal evidence of carcinogenic activity of turmeric oleoresin in male B6C3F1 mice based on a marginally increased incidence of hepatocellular adenoma at the 10,000 ppm level, and the occurrence of carcinomas of the small intestine in the 2,000 and 10,000 ppm groups. There was equivocal evidence of carcinogenic activity of turmeric oleoresin in female B6C3F1 mice based on an increased incidence of hepatocellular adenomas in the 10,000 ppm group. Turmeric oleoresin ingestion was also associated with increased incidences of ulcers, hyperplasia, and inflammation of the forestomach, cecum, and colon in male rats and of the cecum in female rats. In female mice, ingestion of diets containing turmeric oleoresin was also associated with an increased incidence of thyroid gland follicular cell hyperplasia. Synonyms for Turmeric Oleoresin: curcuma oil; oil of turmeric; turmeric oil; curcuma longa oils; curcuma long oil; Curcumin Synonyms for Curcumin: 1,7-Bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione; C.I. Natural Yellow 3; C.I. 75300; Curcuma; diferuloylmethane; E 100; Haidr; Halad; Haldar; Halud; HSDB 4334; Indian Saffron; kacha haldi; Kurkumin; merita earth; Souchet; Turmeric Yellow; yellow ginger; yellow root; Yo-kin; Zlut Prirodni 3; NCI-C613253

Journal Article↗
PubMed1993

Toxicology and Carcinogenesis Studies of 5,5-Diphenylhydantoin (CAS No. 57-41-0) (Phenytoin) in F344/N Rats and B6C3F1 Mice (Feed Studies).

5,5-Diphenylhydantoin and its sodium salt are primarily used in the treatment of grand mal and psychomotor seizures, often in combination with other anticonvulsants, including phenobarbital. 5,5-Diphenylhydantoin is a suspected human carcinogen and was one of three compounds selected by the NTP to investigate the potential value of perinatal exposures in assessing chemical carcinogenicity. Chronic toxicity and carcinogenicity studies of 5,5-diphenylhydantoin were conducted in male and female F344/N rats and B6C3F1 mice. The studies were designed to determine the following: a) the effects of 5,5-diphenylhydantoin in the diet given to rats and mice during the adult (F1) period only (a typical carcinogenicity study), b) the toxic and carcinogenic effects of 5,5-diphenylhydantoin in rats and mice receiving perinatal (F0) exposure only (dietary exposure of dams prior to breeding and throughout gestation and lactation), and c) the effects of combined perinatal and adult exposure to 5,5-diphenylhydantoin. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse Iymphoma cells, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse bone marrow cells. STUDIES IN F344/N RATS: A 13-week toxicity study was conducted to select the exposure levels for adults in the 2-year study. The exposure levels for the 13-week study ranged from 300 to 4,800 ppm 5,5-diphenylhydantoin in the diet. The final mean body weights of males and females exposed to 2,400 or 4,800 ppm were significantly decreased. All groups showed a net weight gain over the study period, although the mean body weight gain of females in the 4,800 ppm group was only one-half that of the controls. Feed consumption also decreased with increasing exposure level. No chemical-related gross lesions were present in the tissues of exposed rats. Microscopically, centrilobular hypertrophy of hepatocytes was observed in the liver of rats in the 4,800 ppm groups. Based on these results, 2,400 ppm was selected as the highest exposure for the adult-only portion of the 2-year carcinogenicity study. A gestational study was performed to select the exposure levels for the perinatal portion of the 2-year study. The exposure levels ranged from 80 to 2,400 ppm 5,5-diphenylhydantoin in the diet of the dams. The 2,400 ppm exposure level was found to have reproductive and embryotoxic effects, as none of the sperm-positive females delivered litters. In the 800 ppm group, a greater number of pups died between postnatal day 1 and day 28 than in the control group. No gross external malformations were observed among fetuses or pups surviving to term in any exposure group, and no gross or histopathologic lesions were observed in the animals exposed to 800 ppm for 4 weeks following weaning. Based on these results, 630 ppm was selected as the highest exposure level for the perinatal portion of the 2-year carcinogenicity study. The eight F0:F1 exposure combinations selected for the 2-year study are listed in the table (contained in full report - page 6). In the 2-year study, male and female rats in the 630:2,400 ppm groups evaluated at 9 months had increased relative liver weights. Hematologic evaluations indicated mild but consistent chemical-related increases in erythrocyte and platelet counts in male and female rats. Mild decreases in triglyceride concentrations and alanine aminotransferase enzyme activity were seen generally in the high-exposure groups. In the 2-year study, the survival of exposed rats was similar to that of the controls. However, body weights of exposed rats were lower than those of the controls, and body weights were 11% to 35~ lower in rats receiving adult exposure of 2,400 ppm 5,5-diphenylhydantoin. Feed consumption was similar for exposed and control groups. Hepatocellular neoplasms, primarily adenomas, occurred with a positive trend in male rats fed 5,5-diphenylhydantoin only as adults (0:0 ppm, 0/50; 0:800 ppm, 2/50; 0:2,400 ppm, 4/50). There were no increased neoplasm incidences at other sites in exposed males or at any site in exposed females.emales. Perinatal-only or combined perinatal and adult exposure to 5,5-diphenylhydantoin did not enhance the overall incidences of liver neoplasms in male or female rats. However, the finding of 5/49 hepatocellular adenomas in the 630:2,400 male rat group was consistent with the marginally elevated liver neoplasm rate observed in the 0:2,400 group. Decreased incidences of a number of different neoplasms in exposed groups were most likely related to the lower body weights. STUDIES IN B6C3F1 MICE: A 13-week toxicity study was conducted to select the exposure levels for adults in the 2-year study. The exposure levels for the 13-week study ranged from 75 to 1,200 ppm 5,5-diphenylhydantoin in the diet. With the exception of one male, all mice exposed to 1,200 ppm died before the end of the study. No other chemical-related deaths occurred. All groups of mice except the 1,200 ppm groups gained weight over the 13-week period; however, an exposure related decrease in body weight gain was seen in males and females. Feed consumption by exposed and control groups was generally similar. Chemical related histomorphologic lesions were present in the liver of exposed mice, particularly 600 ppm males, and consisted of centrilobular hypertrophy of hepatocytes. Females appeared to be less sensitive than males to the effects of 5,5-diphenylhydantoin on growth and on histomorphologic liver lesions. Based on these results, 300 ppm (males) and 600 ppm (females) were selected as the highest exposure levels for the adult-only portion of the 2-year carcinogenicity study. A gestational study was performed to select the exposure levels for the perinatal portion of the 2-year study. The exposure levels for males and females ranged from 20 to 600 ppm 5,5-diphenylhydantoin in the diet. In general, reproductive performance and maternal care were poor in all groups, including the controls, thus restricting the sample size and sensitivity of this evaluation. There were no litters in the 600 ppm group, and maternal weight gain was depressed. There were no gross external malformations among pups surviving to term, and no gross or histopathologic lesions were observed in any mice exposed for 4 weeks following weaning. Based on these results, 210 ppm was selected as the highest exposure level for the perinatal portion of the 2-year carcinogenicity study. The F0:F1 exposure combinations selected for the 2-year study are listed in the following table (contained in full report - page 7). For mice evaluated at 9 months, males and females receiving the highest F0:F1 exposure levels had increased relative liver weights. In the 2-year study, the survival of exposed animals was similar to that of the controls; however, body weights were lower for exposed groups, and decreased body weights were most severe in adult females receiving 600 ppm 5,5-diphenylhydantoin. Feed consumption was similar for exposed and control groups. The incidences of hepatocellular neoplasms were increased in female mice receiving adult-only exposure (0:0 ppm, 5/48; 0:200 ppm, 14/49; 0:600 ppm, 30/50) or combined perinatal and adult exposure (210:200 ppm, 16/50; 210:600 ppm, 34/50). A marginally increased incidence of liver neoplasms (12/49) occurred in females in the perinatal-only (210:0) exposure group. There were no chemical-related increased incidences of liver neoplasms in males receiving adult-only or perinatal-only exposure. However, males receiving the high-exposure combined perinatal and adult exposure regimen (210:300 ppm) had an increased incidence of liver neoplasms (41/50) compared to the 0:0 (29/50), 0:300 (26/49), and 210:0 (33/50) groups. As a result, there was a significant enhancement (interaction) associated with combined perinatal and adult exposure. Such enhancement of neoplasia did not occur in female mice. Decreased incidences of malignant neoplasms in exposed groups were most likely related to the lower body weights. GENETIC TOXICOLOGY: In general, tests for genotoxic activity of 5,5-diphenylhydantoin were negative. All in vitro testing was performed in the presence and the absence of exogenous metabolic activation (S9). 5,5-Diphenylhydantoin did not induce mutations in Salmonella typhimurium, in L5178Y mouse Iymphoma cells, or in germ cells of male Drosophila melanogaster, nor did it induce chromosomal aberrations in cultured Chinese hamster ovary cells. A small but statistically significant increase was obtained in the cultured Chinese hamster ovary cell test for induction of sister chromatid exchanges in the presence of S9; without S9, no increase in sister chromatid exchanges was observed. In vivo, 5,5-diphenylhydantoin did not induce micronuclei polychromatic erythrocytes or chromosomal aberrations in bone marrow cells of male mice; equivocal results were obtained in an in vivo test for induction of sister chromatid exchanges in mouse bone marrow cells. CONCLUSIONS: Adult-Only Exposure: Under the conditions of these 2-year, adult-only, dietary exposure studies, there was equivocal evidence of carcinogenic activity of 5,5-diphenylhydantoin in male F344/N rats based on marginally increased incidences of hepatocellular neoplasms. There was no evidence of carcinogenic activity of 5,5-diphenylhydantoin in female F344/N rats given 240, 800, or 2,400 ppm. There was no evidence of carcinogenic activity of 5,5-diphenylhydantoin in male B6C3F1 mice given 30,100, or 300 ppm. There was clear evidence of carcinogenic activity of 5,5-diphenylhydantoin in female B6C3F1 mice based on increased incidences of hepatocellular neoplasms. Perinatal-Only Exposure: Perinatal exposure alone (through dietary administration of 210 ppm 5,5-diphenylhydantoin during the perinatal period) caused a marginal increase in the incidences of hepatocellular neoplasms in female B6C3F1 mice evaluated 2 years after cessation of exposure. In male and female F344/N rats, exposure to 630 ppm during the perinatal period did not influence the incidences of hepatocellular or other neoplasms. Similarly, exposure of male B6C3F1 mice to dietary levels of 210 ppm 5,5-diphenylhydantoin during the perinatal period did not affect neoplasm incidences. No teratologic effects were observed. Combined Perinatal and Adult Exposure: Combined perinatal and adult dietary exposure to 5,5-diphenylhydantoin confirmed the findings of the increased incidences of hepatocellular neoplasms for adult-only exposures in male F344/N rats and female B6C3F1 mice, although combined exposure did not enhance these neoplastic effects. However, in male B6C3F1 mice, combined perinatal and adult exposure resulted in increased incidences of hepatocellular neoplasms (hepatocellular carcinomas and multiple adenomas) that were not seen when dietary exposure was limited to the adult exposure period only. Synonyms: Diphenylhydantoin; 5,5-diphenyl-2,4-imidazolidinedione Trade names: Difhydan; Dihycon; Di-Hydan; Di-Lan; Dilabid; Dilantin; Ekko; Hydantol; Lehydan; Zentropil

Journal Article↗
PubMed1993

Toxicology and Carcinogenesis Studies of Furan (CAS No. 110-00-9) in F344 Rats and B6C3F1 Mice(Gavage Studies).

Furan serves as an intermediate in the synthesis and preparation of numerous linear polymers used to prepare temperature-resistant structural laminates and to prepare copolymers used in machine dishwashing products as alternatives to phosphorus- and nitrogen-containing detergents. Toxicology and carcinogenesis studies were conducted by administering furan (purity > 99%) in corn oil by gavage to groups of F344/N rats and B6C3F1 mice of each sex for 16 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Drosophila melanogaster, mouse bone marrow cells, mouse L5178Y lymphoma cells, and Chinese hamster ovary cells. 16-Day Studies: Groups of five male rats received doses of 0, 5, 10, 20, 40, or 80 mg of furan per kg of body weight and groups of five female rats and five mice of each sex received doses of 0, 10, 20, 40, 80, and 160 mg/kg in corn oil by gavage. All male and female mice and female rats that received 160 mg/kg, all male and female rats and all male and four female mice that received 80 mg/kg, and three male mice that received 40 mg/kg died by day 8. Final mean body weights of male rats that received 20 mg/kg and of male and female rats that received 40 mg/kg were significantly lower than controls. Final mean body weights of male mice that received 10 or 20 mg/kg were significantly greater than controls. Mottled and enlarged livers were observed at necropsy in male rats that received 20, 40, or 80 mg/kg and in females that received 40, 80, or 160 mg/kg. No lesions were observed at necropsy that were considered related to furan administration in mice. 13-Week Studies: Groups of 10 rats of each sex and groups of 10 female mice received doses of 0, 4, 8, 15, 30, or 60 mg of furan per kg of body weight, and groups of 10 male mice received doses of 0, 2, 4, 8, 15, or 30 mg/kg in corn oil by gavage. Nine male and four female rats that received 60 mg/kg died before the end of the studies. There were no chemical-related deaths in mice. Final mean body weights of male rats that received 15 or 30 mg/kg and female rats that received 60 mg/kg were significantly lower than controls. Final mean body weights of male mice that received 60 mg/kg were significantly lower than controls. Relative and absolute liver weights in both sexes of rats and mice were increased in groups that received furan, as were relative and absolute kidney weights in female rats that received furan. Thymus weights were decreased in all groups of rats that received furan. Toxic lesions of the liver (bile duct hyperplasia, cholangiofibrosis, cytomegaly and degeneration of hepatocytes, and nodular hyperplasia of hepatocytes) were associated with furan administration in all dose groups of rats; the severity of the lesions increased with dose. Kidney lesions (tubule dilatation and necrosis of tubule epithelium) were present in rats that received 30 or 60 mg/kg. Thymic atrophy and testicular or ovarian atrophy were also observed in rats exposed to 60 mg/kg furan. Toxic liver lesions (cytomegaly, degeneration, and necrosis of hepatocytes) were also present in all groups of furan-exposed mice. Bile duct hyperplasia and cholangiofibrosis were observed in groups of mice receiving 30 or 60 mg/kg. Doses selected for the 2-year studies of rats and mice were based on the hepatotoxicity associated with exposure to furan. 2-Year Studies: Groups of 70 rats of each sex were administered 2, 4, or 8 mg furan per kg body weight in corn oil by gavage 5 days per week for 2 years. After 9 and 15 months of chemical exposure, 10 rats per group were evaluated for the presence of treatment-associated lesions. Groups of 50 mice of each sex received doses of 8 or 15 mg/kg furan 5 days per week for 2 years. Body Weight and Survival: Mean body weights of male rats that received 8 mg/kg furan were lower than controls from approximately week 73 to the end of the study. Survival of male and female rats that received 8 mg/kg was lower than controls from approximately week 85 to the end of the studies as a result of moribund condition associatedassociated with liver and biliary tract neoplasms and mononuclear cell leukemia. Mean body weights of male and female mice that received 15 mg/kg furan were lower than controls during the studies. Survival of low- and high-dose male and high-dose female mice was lower than controls from approximately week 80 to the end of the studies as a result of moribund condition associated with liver neoplasms. Neoplastic and Nonneoplastic Lesions: Cholangiocarcinoma of the liver occurred in all groups of dosed rats (males: control, 0/50; low dose, 43/50; mid dose, 48/50; high dose, 49/50; females: 0/50; 49/50; 50/50; 48/50) and was present in many rats of each sex at the 9- and 15-month interim evaluations (9-month: males - 0/10, 5/10, 7/10, 10/10; females - 0/10, 4/10, 9/10, 10/10; 15-month: males - 0/10, 7/10, 9/10, 6/10; females - 0/10, 9/10, 9/10, 7/10). Hepatocellular adenomas or carcinomas (combined) were significantly increased in male rats after 2 years of chemical administration (1/50, 5/50, 22/50, 35/50) and hepatocellular adenomas were significantly increased in female rats (0/50, 2/50, 4/50, 7/50); hepatocellular neoplasms were not observed at the 9- or 15-month interim evaluations. Increased incidences of numerous nonneoplastic liver lesions were present in rats administered furan. These lesions included biliary tract fibrosis, hyperplasia, chronic inflammation, and proliferation and hepatocyte cytomegaly, cytoplasmic vacuolization, degeneration, nodular hyperplasia, and necrosis. The incidence of mononuclear cell leukemia was increased in male and female rats that received 4 or 8 mg/kg furan (males: 8/50, 11/50, 17/50, 25/50; females: 8/50, 9/50, 17/50, 21/50); the incidence in the 8 mg/kg groups of each sex exceeded the historical control ranges for corn oil gavage studies. The severity of nephropathy increased with dose and the incidence was significantly increased in all groups of dosed rats; this increased severity was accompanied by an associated increased incidence of parathyroid hyperplasia (renal secondary hyperparathyroidism). The incidence of forestomach hyperplasia was increased in male and female rats (males: 1/50, 4/49, 7/50, 6/50; females: 0/50, 2/50, 5/50, 5/50) and the incidence of subacute inflammation of the forestomach was increased in female rats (0/50, 1/50, 5/50, 6/50). No forestomach neoplasms were observed in males; a squamous papilloma was present in one low-dose female. The incidences of hepatocellular adenomas and carcinomas were significantly increased in mice receiving furan (males: adenoma - 20/50, 33/50, 42/50; carcinoma - 7/50, 32/50, 34/50; females: adenoma - 5/50, 31/50, 48/50; carcinoma - 2/50, 7/50, 27/50). The incidences of numerous nonneoplastic hepatocellular lesions were increased in dosed mice. These lesions included hepatocyte cytomegaly, degeneration, necrosis, multifocal hyperplasia, and cytoplasmic vacuolization and biliary tract dilatation, fibrosis, hyperplasia, and inflammation. The incidences of benign pheochromocytoma and focal hyperplasia of the adrenal medulla were increased in low- and high-dose male and in high-dose female mice (benign pheochromocytoma: males - 1/49, 6/50, 10/50; females - 2/50, 1/50, 6/50). The incidences of squamous papilloma, focal inflammation, and papillary hyperplasia of the forestomach were increased in male mice (squamous papilloma: 0/49, 1/50, 3/50; focal inflammation: 9/49, 13/50, 21/50; papillary hyperplasia: 7/49, 14/50, 22/50). Stop-Exposure Study: A separate 2-year study was conducted in which 50 male rats were administered 30 mg/kg furan in corn oil by gavage 5 days per week for 13 weeks and then maintained for the remainder of the 2 years without additional furan administration. Groups of 10 animals were evaluated for the presence of treatment-related lesions at the end of the 13-week period of furan administration and at 9 and 15 months. Neoplastic and Nonneoplastic Lesions: Cholangiocarcinoma of the liver occurred with an overall incidence of 100&percnt; (40/40) and hepatocellular carcinoma occurred with an overall incidence of 15&percnt; (6/40) in stop-exposure male rats that survived at least 9 months. Cholangiocarcinoma was observed in all 10 males at both the 9-month and 15-month interim evaluations. Hepatocellular carcinoma was first observed in 2 males at the 15-month interim evaluation. Genetic Toxicology: Furan was negative for induction of gene mutations in Salmonella typhimurium strains TA100, TA1535, TA1537, and TA98 in the presence and the absence of exogenous metabolic activation (S9). Furan was negative for the induction of sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster when administered either by feeding or by injection. In vitro tests for genotoxicity in mammalian cells, however, were positive. Furan induced trifluorothymidine resistance in mouse L5178Y lymphoma cells in the absence of S9, and sister chromatid exchanges and chromosomal aberrations in Chinese hamster ovary cells, with and without S9. Furan administered to male B6C3F1 mice by intraperitoneal injection induced chromosomal aberrations but not sister chromatid exchanges in bone marrow cells. Conclusions: Under the conditions of these 2-year gavage studies there was clear evidence of carcinogenic activity of furan in male and female F344/N rats based on increased incidences of cholangiocarcinoma and hepatocellular neoplasms of the liver and on increased incidences of mononuclear cell leukemia. There was clear evidence of carcinogenic activity of furan in male and female B6C3F1 mice based on increased incidences of hepatocellular neoplasms of the liver and benign pheochromocytomas of the adrenal gland. Nonneoplastic liver lesions associated with furan administration in rats and mice included biliary tract fibrosis, hyperplasia, inflammation, and proliferation, as well as hepatocellular cytomegaly, degeneration, hyperplasia, necrosis, and vacuolization. In rats, increased severity of nephropathy with an associated increased incidence of parathyroid hyperplasia was associated with exposure to furan. Synonyms: Divinylene oxide, tetrole, furfuran, oxole, 1,4-epoxy-1,3-butadiene, axole, oxacyclopentadiene

Journal Article↗
PubMed1993

Toxicology and Carcinogenesis Studies of Mercuric Chloride (CAS No. 7487-94-7) in F344 Rats and B6C3F1 Mice (Gavage Studies).

Mercuric chloride is an inorganic compound that has been used in agriculture as a fungicide, in medicine as a topical antiseptic and disinfectant, and in chemistry as an intermediate in the production of other mercury compounds. The widespread use of mercury has resulted in increased levels of mercury in rivers and lakes. Mercuric chloride was evaluated in toxicity and carcinogenicity studies because of its extensive use and its occurrence as an environmental pollutant, and because of the lack of adequate long-term rodent studies. Toxicology and carcinogenesis studies were conducted by administering mercuric chloride (greater than 99% pure) in deionized water by gavage to groups of F344 rats or B6C3F1 mice for 16 days, 6 months, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium (strains TA98, TA100, TA1535, and TA1537), in mouse lymphoma L5178Y cells, in Chinese hamster ovary cells, and in Drosophila melanogaster. 16-DAY STUDIES: Groups of five rats of each sex received 0, 1.25, 2.5, 5, 10, or 20 mg mercuric chloride/kg body weight and groups of five mice of each sex received 0, 5, 10, 20, 40, or 80 mg/kg in deionized water by gavage for 12 dose days. Two male rats in the 20 mg/kg group died in the first week, as did all male and four female mice from the 80 mg/kg group and one male mouse from the 40 mg/kg group. The final mean body weight of male rats receiving 20 mg/kg was 10% lower than that of the controls; the final mean body weight of 20 mg/kg females was 9% lower than that of the controls. Final mean body weights and body weight gains of dosed mice were similar to those of the controls. Absolute and relative kidney weights of male rats receiving 2.5 mg/kg or greater doses and of female rats administered 5 mg/kg or more were significantly greater than those of the controls. Absolute kidney weights of mice were significantly increased in all male dose groups and in the 40 mg/kg female dose group; relative kidney weights of dosed male and female mice were significantly greater than the controls. Analysis of kidney, liver, and brain tissues for mercury residues revealed that the highest mercury concentration was in the kidneys of rats and mice. Acute renal tubule nephropathy occurred in dosed rats and was slightly more severe in males than in females. Chemical-related lesions in mice included renal tubule necrosis, inflammation and necrosis of the forestomach, and necrosis of the glandular stomach. 6-MONTH STUDIES: Groups of 10 rats of each sex received 0, 0.312, 0.625, 1.25, 2.5, or 5 mg mercuric chloride/kg body weight in deionized water by gavage for 26 weeks. Groups of 10 mice of each sex received 0, 1.25, 2.5, 5, 10, or 20 mg/kg in deionized water by gavage for 26 weeks (males) or 27 weeks (females). No deaths related to mercuric chloride administration occurred in rats or mice. Mean body weight gains of male rats that received 5 mg/kg and all female rat dose groups that received 0.625 mg/kg or greater were significantly lower than the controls. The final mean body weight and body weight gain of male mice in the 20 mg/kg group were significantly lower than those of the controls; final mean body weights and body weight gains of other dosed male mice and all dosed female mice were similar to those of the controls. Absolute and relative kidney weights of all dosed male rats and of female rats that received 0.625 mg/kg or greater were significantly greater than those of the controls. In male mice, absolute kidney weights in the three highest dose groups were significantly increased; no biologically significant differences in organ weights occurred in female mice. Analysis of kidney, liver, and brain tissues for mercury residues revealed the highest mercury concentration in the kidneys of rats and mice. The severity of chronic nephropathy increased with dose in male rats. Cytoplasmic vacuolation of renal tubule epithelial cells was observed in male mice in the 5, 10, and 20 mg/kg groups. No histopathologic changes in female mice were related to chemical exposure. 2-YEAR STUDIES: Groups YEAR STUDIES: Groups of 60 rats of each sex received 0, 2.5, or 5 mg mercuric chloride/kg body weight and groups of 60 mice of each sex received 0, 5, or 10 mg/kg in deionized water by gavage 5 days per week for 2 years. The doses were based on decreased weight gains in rats receiving 10 and 20 mg/kg and the decreased weight in male mice receiving 40 mg/kg during the 16-day studies, and on the decreased weight gains and toxicity results seen in the 6-month studies. Increased absolute and relative kidney weights in rats and male mice in the 6-month studies and degenerative renal changes suggested that higher dose levels would result in inadequate survival rates for a 2-year study. 15-Month Interim Evaluations: Relative kidney weights were significantly increased in dosed rats and female mice. The severity of nephropathy was increased in male rats, but not in females. High-dose male and female rats had minimal to mild hyperplasia of the basal cell layer in the forestomach epithelium (diagnosed as acanthosis); this lesion was not found in control or low-dose rats. Male mice had an increased severity of vacuolation of the renal tubule epithelium; no chemical-related lesions occurred in the kidneys of females. The incidence of inflammation of the olfactory epithelium lining the nasal cavity increased in male and female high-dose mice. Survival, Body Weights, and Clinical Signs: Survival of dosed male rats was lower than that of the controls (26/50, 10/50, 5/50); survival of dosed female rats was similar to that of the controls (35/50, 28/49, 30/50). Although more than 60&percnt; of the mice in each dose group survived to study end, survival rates of high-dose male mice and dosed female mice were lower than those of the controls (males: 36/50, 36/50, 31/50; females: 41/50, 35/50, 31/50). The final mean body weights of high-dose male and female rats were 15&percnt; and 14&percnt; lower than controls, respectively. The mean body weight of low-dose female rats was generally similar to controls throughout the 2-year study; the mean body weight of low-dose male rats was similar to that of the control through week 89. In mice, mean body weights of all male and female dose groups were similar to those of the controls throughout the studies. Pathology Findings: Chronic nephropathy appeared to develop at an accelerated rate and led to decreased survival in both dosed male rat groups. Secondary effects of renal dysfunction in dosed male rats resulted in increased incidences of fibrous osteodystrophy of the bone, mineralization of various tissues, and parathyroid gland hyperplasia. Based on evaluations of single and step sections, the incidence of renal tubule hyperplasia was increased in high-dose male rats (control, 3/50; high-dose, 10/50), but the incidences of renal tubule adenoma in high-dose and control males were similar (4/50, 5/50). Renal tubule hyperplasia was also slightly increased in high-dose female rats (2/50, 5/50) and adenomas were seen in high-dose females, but not in controls (0/50, 2/50). Incidences of forestomach hyperplasia in rats were markedly increased in dosed males (3/49, 16/50, 35/50) and high-dose females (5/50, 5/49, 20/50). Squamous cell papillomas of the forestomach were found in 3 low-dose and 12 high-dose males and in 2 high-dose females. No squamous cell carcinomas were found. The incidence of thyroid follicular cell carcinoma was marginally increased in high-dose male rats (1/50, 2/50, 6/50). However, a corresponding increased incidence in follicular cell adenomas (1/50, 4/50, 0/50) or hyperplasia (2/50, 4/50, 2/50) in males did not occur, and the overall incidence of follicular cell neoplasms was not significantly increased (2/50, 6/50, 6/50). The incidence of nasal mucosa inflammation in male and female rats was increased in the high-dose groups (male: 9/50, 8/47, 18/50; female: 0/49, 5/49, 15/50) and may have been related to chemical administration. The incidences of mammary gland fibroadenomas were significantly decreased in dosed female rats (15/50, 5/48, 2/50). The incidence and severity of nephropathy were increased in dosed mice; secondary effects of renal dysfunction did not occur. Renal tubule hyperplasia was found in one control and two high-dose male mice. Two renal tubule adenomas and one renal tubule adenocarcinoma were seen in high-dose male mice. Additional step sections revealed focal hyperplasia in another control male; no additional renal tubule neoplasms were found in high-dose or control males. Proliferative lesions of the renal tubule epithelium were not found in female mice. The incidence of metaplasia of the olfactory epithelium increased with dose in male and female mice. No other biologically significant lesions were found. GENETIC TOXICOLOGY: Mercuric chloride was not mutagenic in Salmonella typhimurium strains TA100, TA1535, TA1537, or TA98 with or without exogenous metabolic activation (S9). Induction of sex-linked recessive lethal mutations in germ cells of male Drosophila melanogaster did not occur when mercuric chloride was administered in feed or by injection. However, positive results were obtained in mutagenicity tests with mammalian cells. In the absence of S9, mercuric chloride induced trifluorothymidine resistance in mouse L5178Y cells and chromosomal aberrations in Chinese hamster ovary cells. In the Chinese hamster ovary cell test for induction of sister chromatid exchanges, mercuric chloride produced a negative response without S9 and a weakly positive response in the presence of S9. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of mercuric chloride in male F344 rats based on the increased incidence of squamous cell papillomas of the forestomach. Marginally increased incidences of thyroid follicular cell adenomas and carcinomas may have been related to mercuric chloride exposure. There was equivocal evidence of carcinogenic activity of mercuric chloride in female F344 rats based on two squamous cell papillomas of the forestomach. There was equivocal evidence of carcinogenic activity of mercuric chloride in male B6C3F1 mice based on the occurrences of two renal tubule adenomas and one renal tubule adenocarcinoma. There was no evidence of carcinogenic activity of mercuric chloride in female B6C3F1 mice receiving 5 or 10 mg/kg. Nonneoplastic lesions associated with exposure to mercuric chloride included increased severity of nephropathy in male rats and male and female mice. There was an increased incidence of renal tubule hyperplasia in male rats. The incidence of forestomach hyperplasia was increased in dosed male and female rats. Increased incidences of nasal mucosa inflammation were associated with mercuric chloride administration in rats. Increased incidences of olfactory epithelial metaplasia in mice were also associated with mercuric chloride administration. Synonyms: Abavit B, calochlor, corrosive sublimate, dichloromercury, mercuric bichloride, mercury chloride, mercury (II) chloride, mercury bichloride, mercury perchloride, sublimate, sulem, bichloride of mercury, corrosive mercury chloride, perchloride of mercury, mercury dichloride Trade name: Fungchex

Journal Article↗
PubMed1993

NTP Toxicology and Carcinogenesis Studies of Polybrominated Biphenyls (CAS No. 67774-32-7)(Firemaster FF-1(R)) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Polybrominated biphenyls are synthetic chemicals used as flame retardants. The technical product used in these studies, Firemaster FF-1(R)), is a mixture of brominated biphenyls. Firemaster FF-1(R)) is a known liver carcinogen in rats and mice and is one of three compounds chosen by the National Toxicology Program to investigate the potential value of perinatal exposures in assessing chemical carcinogenicity. Chronic toxicity and carcinogenicity studies of polybrominated biphenyls (Firemaster FF-1(R)) were conducted in F344/N rats and B6C3F1 mice of each sex. The studies were designed to determine: a) the effects of polybrominated biphenyls in rats and mice receiving adult ( F1) exposure only (a typical carcinogenicity study), b) the toxic and carcinogenic effects of polybrominated biphenyls in rats and mice receiving perinatal (F0) exposure only (dietary exposure of dams prior to breeding and throughout gestation and lactation), and c) the effects of combined perinatal and adult exposure to polybrominated biphenyls. STUDIES IN F344/N RATS: The exposure levels selected for F1 exposure, based on studies of polybrominated biphenyls in the literature, were 3, 10, and 30 ppm. In a preliminary study to determine the perinatal dietary concentrations for the 2-year study, female rats were administered 1 to 30 ppm polybrominated biphenyls in the feed beginning 60 days prior to breeding and continuing throughout gestation, lactation, and up to 4 weeks postweaning. The mean preweaning litter weight of the 30 ppm group was less than 80% of the mean litter weight of the control group at days 0, 4, and 12. At weaning, the mean weight of litters in this group was 80% of the control group mean. The final mean body weights (28 days after weaning) of males and females receiving 30 ppm were 13% to 19% lower than the final mean body weights of the controls. Therefore, dietary concentrations of 0, 1, 3, and 10 ppm were selected for the F0 exposure levels in the 2-year study. The eight F0 F1 exposure combinations selected for the 2-year study are shown in the following table (see page 6 of full technical report). Adult-Only Exposure The major organ affected by toxicity of polybrominated biphenyls was the liver. Rats evaluated at 9 months had decreased body weights, hepatomegaly, nonneoplastic histopathologic changes in the liver, mild anemia, increases in serum cholesterol concentrations, and decreases in serum triglyceride concentrations (males only). In rats receiving adult only exposure (F0 F1 concentrations of 0:10 or 0:30 ppm), there were no significant effects on survival. Mean body weights were significantly reduced in 0:10 and 0:30 ppm male rats and in 0:30 ppm female rats. Males and females exposed to 0:10 or 0:30 ppm had increased incidences of hepatocellular neoplasms (males: 0:0 ppm, 1/50; 0:10 ppm, 12/49; 0:30 ppm, 41/50; females: 0/50,12/50, 39/50). Increased incidences of the following nonneoplastic lesions were associated with the administration of polybrominated biphenyls: eosinophilic foci, cytoplasmic vacuolization, oval cell hyperplasia, and hypertrophy in the liver of males and females; acanthosis, inflammation, and ulceration of the forestomach in exposed males; and cystic endometrial hyperplasia of the uterus in 0:30 ppm females. Perinatal-Only Exposure For rats receiving only perinatal exposure (10:0 ppm), there were no changes in survival or body weights compared to the 0:0 ppm control groups. In female rats, there were no effects on neoplasm incidences, but perinatal exposure was associated with a marginally increased incidence of hepatocellular adenoma in male rats (0:0 ppm, 1/50; 10:0 ppm, 5/50). The incidences of nonneoplastic lesions in the liver were increased in exposed males (eosinophilic foci and cytoplasmic vacuolization) and females (eosinophilic foci). Combined Perinatal and Adult Exposure Combined perinatal and adult exposure resulted in marginally reduced survival compared to the 0:0 ppm control group for male rats in the 3:10, 10:10, and 10:30 ppm groups. No significant survival differences were obseant survival differences were observed in female rats. The final mean body weights of male and female rats receiving 3:10,10:10, or 10:30 ppm were lower than those of the 0:0 ppm controls. In male rats, there were no enhancing effects of combined perinatal and adult exposure on the incidence of hepatocellular neoplasms. However, perinatal exposure enhanced the development of liver neoplasms in female rats receiving 10 or 30 ppm adult exposure. A combined analysis of all male and female exposure groups also revealed increased incidences of mononuclear cell leukemia that were considered related to polybrominated biphenyls exposure. STUDIES IN B6C3F1 MICE: The exposure levels selected for the F1 exposure, based on studies of polybrominated biphenyls in the literature, were 3,10, and 30 ppm. In a preliminary study to determine the perinatal dietary concentrations for the 2-year study, female C57BL/6N mice were exposed to 1 to 30 ppm polybrominated biphenyls in the feed beginning 60 days before breeding to C3H/HeN males, continuing throughout gestation and lactation and up to 4 weeks postweaning. There were no clear chemical-related effects on survival or growth at any phase of the study; therefore, 0, 3,10, and 30 ppm dietary concentrations were selected for the F0 exposure levels in the 2-year study. The eight F0 F1 exposure combinations selected for the 2-year study are shown in the table below (see page 7 of full technical report). Adult-Only Exposure The major organ affected by toxicity of polybrominated biphenyls was the liver. Animals evaluated at 9 months had lower body weights than the controls, hepatomegaly, and histopathologic changes in the liver. In mice receiving adult-only exposure, no males or females in the 0:30 ppm group survived to the end of the study. Neither survival nor body weights were affected in the 0:10 ppm groups. Males and females receiving 0:10 or 0:30 ppm had markedly increased incidences of hepatocellular neoplasms (males: 0:0 ppm, 16/50; 0:10 ppm, 48/49; 0:30 ppm, 48/50; females: 5/50, 42/50, 47/48). Increased incidences of nonneoplastic liver lesions including cytomegaly (hypertrophy), fatty change (cytoplasmic vacuolization), bile duct hyperplasia, eosinophilic and clear cell foci, and necrosis of individual hepatocytes were related to treatment with polybrominated biphenyls. Increased incidences and severity of chronic nephropathy in the kidney and excessive hematopoiesis in the spleen of 0:30 ppm males and females were also considered to be related to exposure to polybrominated biphenyls. Perinatal-Only Exposure There were no survival or body weight differences in mice receiving only perinatal exposure (30:0 ppm). Perinatal exposure resulted in significantly increased incidences of hepatocellular neoplasms in males and females. The incidences of nonneoplastic lesions (cytomegaly, eosinophilic foci, clear cell foci) were increased in males and females. Combined Perinatal and Adult Exposure Combined perinatal and adult exposure resulted in markedly reduced survival for females in the 30:10 ppm group; no mice receiving 30:30 ppm survived to the end of the study. In those groups receiving adult exposure of 30 ppm, mean body weights were not affected. The incidence of hepatocellular neoplasms in male and female mice was significantly increased. At the 9-month interim evaluation the incidence of hepatocellular adenomas was significantly increased in males (0:30 ppm, 1/10; 30:30 ppm, 7/10). The incidence of hepatocellular adenomas in 30:30 ppm females was similar to that of 0:30 ppm females (0:30 ppm, 0/10; 30:30 ppm, 3/10). At the end of the study the incidence of hepatocellular adenomas in males was statistically increased (0:30 ppm, 42/50; 30:30 ppm, 48/50). The incidence of hepatocellular adenomas in 30:30 ppm females was statistically decreased compared to that of 0:30 ppm females (0:30 ppm, 46/48; 30:30 ppm, 41/47). It was not possible to assess the potential enhancing effect of combined perinatal and adult exposure on hepatocellular neoplasms because adult-only exposure resulted in such high (84&percnt; to 98&percnt;) liver neoplasm incidences. CONCLUSIONS: Adult-Only Exposure Under the conditions of these 2-year, adult-only, dietary exposure studies, there was clear evidence of carcinogenic activity for polybrominated biphenyls in male and female F344/N rats and male and female B6C3F1 mice based on increased incidences of hepatocellular neoplasms. Perinatal-Only Exposure Perinatal exposure alone (through dietary administration of 10:0 ppm polybrominated biphenyls to the dams) had no effect on the incidences of neoplasms in female F344/N rats, but in male F344/N rats, perinatal exposure was associated with a marginally increased incidence of hepatocellular adenomas that may have been related to chemical administration. In male and female B6C3F1 mice, perinatal exposure to 30:0 ppm polybrominated biphenyls resulted in significantly increased incidences of hepatocellular neoplasms. The incidences of a number of nonneoplastic lesions in the liver (cytomegaly, eosinophilic focus, and clear cell focus) were increased in male and female B6C3F1 mice. Combined Perinatal and Adult Exposure Combined perinatal and adult dietary exposure to polybrominated biphenyls confirmed findings of the adult-only exposures for the increased incidences of hepatocellular neoplasms in F344/N rats and B6C3F1 mice. In male F344/N rats, there were no enhancing effects of combined perinatal and adult exposure. However, perinatal exposure enhanced the susceptibility of female F344/N rats receiving adult exposure of 10 or 30 ppm to the induction of liver neoplasms. For male and female F344/N rats, a combined analysis of the incidences of leukemia in the adult-only, perinatal-only, and combined perinatal and adult exposure groups revealed an apparent association between increasing incidences of mononuclear cell leukemia and exposure to polybrominated biphenyls. In male and female B6C3F1 mice, it was not possible to adequately assess the enhancing effects of combined perinatal and adult exposure on hepatocellular neoplasms, because adult-only exposure to 10 or 30 ppm polybrominated biphenyls resulted in high incidences (84&percnt; to 98&percnt;) of liver neoplasms. However, with increased perinatal exposure, there were increases in the numbers of B6C3F1 mice with hepatocellular carcinomas and in the numbers of B6C3F1 mice with multiple hepatocellular adenomas, which suggests an enhancement of polybrominated biphenyls-related hepatocellular carcinogenicity associated with perinatal exposure. Synonyms: PBBs; polybrominated biphenyl mixture; hexabromobiphenyl (technical grade); brominated biphenyls; polybromobiphenyls

Journal Article↗