Biomedical subjects

National Toxicology Program

Publications and source records attributed to National Toxicology Program.

At least 19 recordsLinked to original sources

PubMed2004

NTP technical report on the toxicology and carcinogenesis studies of propylene glycol mono-t-butyl ether (CAS No. 57018-52-7) in F344/N rats and B6C3F1 mice and a toxicology study of propylene glycol mono-t-butyl ether in male NBR rats (inhalation studies).

BACKGROUND: Propylene glycol mono-t-butyl ether is used as a solvent in all-purpose cleaners, inks, and nail polish lacquers. We studied the effects of propylene glycol mono-t-butyl ether on male and female rats to identify potential toxic or cancer-related hazards to humans. METHODS: We exposed groups of male and female rats and mice to air containing vapors of propylene glycol mono-t-butyl ether at concentrations of 75, 300, or 1,200 parts per million (ppm) for 6 hours per day, 5 days a week for 2 years. Untreated control animals were housed in similar exposure chambers but without chemical exposure for comparison. Tissues from more than 40 sites were examined for every animal. RESULTS: Rats receiving 1,200 ppm propylene glycol mono-t-butyl ether weighed less on average than the control animals. Tumors were seen in the liver and kidney of a few male rats exposed to propylene glycol mono-t-butyl ether. No increases in the numbers of tumors were seen in female rats. In male and female mice there were large increases in the numbers of liver tumors compared with the control animals. CONCLUSIONS: We conclude that propylene glycol mono-t-butyl ether caused cancer in the liver of male and female mice. Propylene glycol mono-t-butyl ether did not cause cancer in female rats, and its effect on the liver and kidney of male rats was considered uncertain.

Administration, Inhalation↗

PubMed2004

NTP toxicology and carcinogenesis studies of trans-cinnamaldehyde (CAS No. 14371-10-9) in F344/N rats and B6C3F1 mice (feed studies).

UNLABELLED: Cinnamaldehyde is used in foods, beverages, medical products, perfumes, cosmetics, soaps, detergents, creams, and lotions. Cinnamaldehyde has been used as a filtering agent and a rubber reinforcing agent and is used as a brightener in electroplating processes, as an animal repellent, as an insect attractant, and as an antifungal agent. trans-cinnamaldehyde was nominated for study by the Food and Drug Administration based on its widespread use as a flavor and fragrance ingredient and its structural similarity to cinnamyl anthranilate and 3,4,5-trimethoxy cinnamaldehyde, two known rodent carcinogens. Male and female F344/N rats and B6C3F1 mice were exposed to trans-cinnamaldehyde (at least 95% pure) in feed for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 4,100, 8,200, 16,500, or 33,000 ppm microencapsulated trans-cinnamaldehyde (equivalent to average daily doses of approximately 275, 625, 1,300, or 4,000 mg trans-cinnamaldehyde/kg body weight to males and 300, 570, 1,090, or 3,100 mg/kg to females) for 3 months. Additional groups of 10 male and 10 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). All rats survived to the end of the study. Mean body weights of all exposed groups of males and 16,500 and 33,000 ppm females were significantly less than those of the vehicle controls, and 33,000 ppm males lost weight during the study. Feed consumption by exposed groups of males and females was less than that by the vehicle controls throughout the study. Clinical chemistry results of these studies indicated that trans-cinnamaldehyde administration, at the doses selected, induced an increase in serum bile acid concentration that suggests a hepatic effect in both male and female rats. Gross lesions observed at necropsy included multifocal to diffuse white nodules of the forestomach mucosa in 8,200 ppm or greater males and females. Increased incidences of nonneoplastic lesions of the forestomach included squamous epithelial hyperplasia in 8,200 ppm or greater males and females and chronic active inflammation in 33,000 ppm males and 16,500 and 33,000 ppm females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 4,100, 8,200, 16,500, or 33,000 ppm microencapsulated trans-cinnamaldehyde (equivalent to average daily doses of approximately 650, 1,320, 2,550, and 5,475 mg/kg to males and 625, 1,380, 2,680, and 5,200 mg/kg to females) for 3 months. Additional groups of 10 male and 10 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). One vehicle control male, one 4,100 ppm male, and one 33,000 ppm male died during the first week of the study due to inanition that resulted from difficulty with the feeder. Five 16,500 ppm and eight 33,000 ppm male mice died during weeks 2 and 3 due to unpalatability of the dosed feed. Mean body weights of all exposed groups of males and of females exposed to 8,200 ppm or greater were significantly less than those of the vehicle controls. Feed consumption by 16,500 and 33,000 ppm mice was less than that by the vehicle controls during weeks 1 and 2. The incidence of squamous epithelial hyperplasia of the forestomach mucosa in 33,000 ppm females was significantly increased, and olfactory epithelial degeneration of the nasal cavity occurred in 16,500 and 33,000 ppm males and females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were fed diets containing 1,000, 2,100, or 4,100 ppm microencapsulated trans-cinnamaldehyde for 2 years. Additional groups of 50 male and 50 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,100, or 4,100 ppm delivered average daily doses of approximately 50, 100, or 200 mg/kg to males and females. Survival of 4,100 ppm males was greater than that of the vehicle controls. Mean body weights of 4,100 ppm males and females were generally less than those of the vehicle controls throughout the study. Feed consumption by 2,100 and 4,100 ppm males and 4,100 ppm females was less than that by the vehicle controls at the beginning and end of the study. There were no neoplasms or nonneoplastic lesions that were attributed to exposure to trans-cinnamaldehyde. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 1,000, 2,100, or 4,100 ppm microencapsulated trans-cinnamaldehyde for 2 years. Additional groups of 50 male and 50 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,100, or 4,100 ppm delivered average daily doses of approximately 125, 270, or 550 mg/kg to males and females. Survival of males in the 2,100 ppm group was less than that of the vehicle control group. Mean body weights of 2,100 and 4,100 ppm males and females were generally less than those of the vehicle controls throughout the study, and mean body weights of 1,000 ppm males were less after week 74. Feed consumption by exposed mice was similar to that by the vehicle controls. The incidences of olfactory epithelial pigmentation in 4,100 ppm males and in 2,100 and 4,100 females were significantly greater than those in vehicle controls. There were no neoplasms that were attributed to exposure to trans-cinnamaldehyde. GENETIC TOXICOLOGY: trans-cinnamaldehyde was mutagenic in S. typhimurium strain TA100 in the presence of induced mouse liver S9 activation enzymes only. All other strain and activation combinations, including the standard rat and hamster derived liver S9 fractions yielded negative results. trans-cinnamaldehyde induced sister chromatid exchanges in Chinese hamster ovary cells with and without induced rat liver S9 activation. No significant increase in the frequency of chromosomal aberrations occurred in Chinese hamster ovary cells cultured with trans-cinnamaldehyde, with or without induced rat liver S9. In tests for induction of germ cell genetic damage in male Drosophila melanogaster, trans-cinnamaldehyde induced a significant increase in the frequency of sex-linked recessive lethal mutations when administered by abdominal injection; however, no induction of reciprocal translocations occurred in germ cells of treated males. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood of male or female mice administered trans-cinnamaldehyde in dosed feed for 3 months. CONCLUSIONS: Under the conditions of this 2-year feed study, there was no evidence of carcinogenic activity of transcinnamaldehyde in male or female F344/N rats exposed to 1,000, 2,100, or 4,100 ppm. There was no evidence of carcinogenic activity of trans-cinnamaldehyde in male or female B6C3F1 mice exposed to 1,000, 2,100, or 4,100 ppm. Exposure to trans-cinnamaldehyde resulted in olfactory epithelial pigmentation in male and female mice.

Acrolein↗

PubMed2003

NTP toxicology and carcinogenesiss studies of citral (microencapsulated) (CAS No. 5392-40-5) in F344/N rats and B6C3F1 mice (feed studies).

UNLABELLED: Citral is used primarily as lemon flavoring in foods, beverages, and candies. It is also used as a lemon fragrance in detergents, perfumes, and other toiletries. Citral was nominated by the National Cancer Institute for study because of its widespread use in foods, beverages, cosmetics, and other consumer products and its structure as a representative beta-substituted vinyl aldehyde. Male and female F344/N rats and B6C3F1 mice were exposed to microencapsulated citral (greater than 96% pure) in feed for 14 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing starch microcapsules with a load of 31.3% citral. The concentration of citral in the diet was 3,900, 7,800, 15,600, or 31,300 ppm microencapsulated citral (equivalent to average daily doses of approximately 345, 820, 1,785, and 1,585 mg citral/kg body weight to males and 335, 675, 1,330, and 2,125 mg/kg to females) for 14 weeks. Additional groups of 10 male and 10 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). In the second week of the study, all rats in the 31,300 ppm groups were killed moribund. Mean body weights of exposed males and females that survived to the end of the study were generally significantly less than those of the vehicle controls. Feed consumption by 15,600 and 31,300 ppm males and females was less than that by the vehicle controls during the first week of the study. Males and females in the 31,300 ppm groups exhibited listlessness, hunched posture, absent or slow paw reflex, and dull eyes. Exposure of rats to citral may have been associated with forestomach epithelial hyperplasia and hyperkeratosis, bone marrow atrophy and hemorrhage, and nephrotoxicity. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 3,900, 7,800, 15,600, or 31,300 ppm microencapsulated citral (equivalent to average daily doses of approximately 745, 1,840, 3,915, and 8,110 mg/kg to males and 790, 1,820, 3,870, and 7,550 mg/kg to females) for 14 weeks. Additional groups of 10 male and 10 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). In the second week of the study, four males in the 31,300 ppm group were killed moribund. Mean body weights of all exposed groups of males and females were significantly less than those of the vehicle controls. Feed consumption by females exposed to 7,800 ppm or greater was less than that by the vehicle controls during the first week of the study. By the end of the study, feed consumption by all exposed groups was greater than that by the vehicle controls. Mice in the 15,600 and 31,300 ppm groups were generally thin and lethargic; a few males in the 7,800 ppm group were also thin. The incidences of ovarian atrophy were significantly increased in females exposed to 15,600 or 31,300 ppm. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were fed diets containing 1,000, 2,000, or 4,000 ppm microencapsulated citral for 2 years. Additional groups of 50 male and 50 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,000, and 4,000 ppm delivered average daily doses of approximately 50, 100, and 210 mg/kg to males and females. Survival of all exposed groups of males was significantly greater than that of the vehicle control group. Mean body weights of rats exposed to 4,000 ppm were generally less than those of the vehicle controls from week 49 (males) or 25 (females) to the end of the study. Feed consumption by exposed groups was similar to that by the vehicle controls. No neoplasms or nonneoplastic lesions were attributed to exposure to citral. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 500, 1,000, or 2,000 ppm microencapsulated citral for 2 years. Additional groups of 50 male and 50 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 500, 1,000, and 2,000 ppm delivered average daily doses of approximately 60, 120, and 260 mg/kg to males and females. Survival of exposed males and females was similar to that of the vehicle control groups. Mean body weights of mice exposed to 1,000 or 2,000 ppm were generally less than those of the vehicle controls throughout the study, and mean body weights of 500 ppm females were less from week 30 to the end of the study. Feed consumption by the exposed groups was similar to that by the vehicle controls. The incidences of malignant lymphoma occurred with a positive trend in female mice, and the incidence in 2,000 ppm females was significantly greater than that in the vehicle control group. Tissues most commonly affected by malignant lymphoma were the spleen, mesenteric lymph node, thymus, and, to a lesser extent, the ovary. GENETIC TOXICOLOGY: Citral was not mutagenic in S. typhimurium strain TA98, TA100, TA1535, or TA1537 with or without induced rat or hamster liver S9 enzymes. In cytogenetic tests with cultured Chinese hamster ovary cells, citral induced sister chromatid exchanges with and without S9, but chromosomal aberrations were not significantly increased after exposure to citral, with or without S9. Negative results were obtained in an in vivo bone marrow micronucleus test in male B6C3F1 mice treated by intraperitoneal injection with 250 to 750 mg/kg daily for 3 days. Likewise, no increases in the frequencies of micronucleated erythrocytes were observed in peripheral blood samples collected from male and female mice within 24 hours of the final exposure in the 14-week study. In conclusion, citral gave negative results in in vitro and in vivo tests for genotoxicity, with the exception of the in vitro mammalian cell test for sister chromatid exchange induction CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of citral in male or female F344/N rats exposed to 1,000, 2,000, or 4,000 ppm. There was no evidence of carcinogenic activity of citral in male B6C3F1 mice exposed to 500, 1,000, or 2,000 ppm. There was equivocal evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of malignant lymphoma.

Acyclic Monoterpenes↗

PubMed2003

Toxicology and carcinogenesis studies of riddelliine (CAS No. 23246-96-0) in F344/N rats and B6C3F1 mice (gavage studies).

UNLABELLED: Riddelliine belongs to a class of toxic pyrrolizidine alkaloids and is isolated from plants of the genera Crotalaria, Amsinckia, and Senecio that grow in the western United States. Cattle, horses, and sheep that ingest these plants succumb to their toxic effects. Riddelliine residues have been found in meat, milk, and honey, and the plants may contaminate human food sources. Riddelliine was nominated for study by the Food and Drug Administration because of its potential for human exposure and its economic impact on the livestock industry and because the toxicity of other pyrrolizidine alkaloids suggests riddelliine may be carcinogenic. Male and female F344/N rats and B6C3F1 mice received riddelliine (approximately 92% pure) by gavage. Female rats and male and female mice were dosed for 2 years; due to high mortality, the study in male rats was terminated at week 72. In vitro genetic toxicology studies were conducted in Salmonella typhimurium and in cultured Chinese hamster ovary (CHO) cells. In addition, riddelliine was evaluated in vivo for induction of micronuclei in mouse bone marrow and peripheral blood erythrocytes and for induction of S-phase DNA synthesis and unscheduled DNA synthesis in the liver of rats and mice. Riddelliine-induced DNA adduct levels were determined in liver tissue obtained from female rats admininstered riddelliine for 3 or 6 months. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0 or 1 mg riddelliine/kg body weight in sodium phosphate buffer by gavage 5 days per week; additional groups of 50 female rats received 0.01, 0.033, 0.1, or 0.33 mg/kg. A wide dose range was used in female rats to better characterize the dose-response curve. Females were dosed for 105 weeks; due to high mortality, male rats were terminated at week 72. All but three 1 mg/kg males died before week 70, and all 1 mg/kg females died before week 97. Mean body weights of 1 mg/kg males and females were less than those of the vehicle controls throughout most of the study. The only clinical finding related to riddelliine administration was a general debilitation of the animals prior to death. Hemangiosarcomas were present in the liver of 86% of males and 76% of females in the 1 mg/kg groups, and this neoplasm was considered the cause of the large number of early deaths in these groups. The incidences of hepatocellular adenoma and mononuclear cell leukemia in 1 mg/kg males and females were significantly increased. Nonneoplastic lesions related to riddelliine treatment occurred in the liver and kidney of males and females. Analyses of liver tissue from female rats treated with riddelliine for 3 or 6 months yielded eight DNA adducts; these were the same as DNA adducts formed in vitro by the metabolism of riddelliine by human liver microsomes in the presence of calf thymus DNA. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered riddelliine in sodium phosphate buffer by gavage at doses of 0 or 3 mg/kg, 5 days per week, for 105 weeks; additional groups of 50 male mice received 0.1, 0.3, or 1 mg/kg for 105 weeks. A wide dose range was used in male mice to better characterize the dose-response curve. Survival of males and females administered 3 mg/kg was significantly less than that of the vehicle controls. Mean body weights of 3 mg/kg mice were less than those of the vehicle controls throughout most of the study. Hemangiosarcomas of the liver were present in 62% of males in the 3 mg/kg group. The incidences of hepatocellular neoplasms occurred with negative trends in male mice and were significantly decreased in 3 mg/kg females. The incidences of alveolar/bronchiolar neoplasms in 3 mg/kg females were significantly increased. Nonneoplastic lesions related to riddelliine administration occurred in the liver and kidney of males and females and in the lung and arteries (multiple tissues) of females. GENETIC TOXICOLOGY: Riddelliine was mutagenic in S. typhimurium strain TA100 with, but not without, S9 activation; no significant mutagenic activity was detected in strain TA98 or TA1535,ed in strain TA98 or TA1535, with or without S9. A small, dose-related increase in mutant colonies seen in strain TA97 with S9 was judged to be equivocal. Riddelliine induced sister chromatid exchanges in cultured CHO cells with and without S9. Chromosomal aberrations were induced in CHO cells only in the presence of S9. Following 4 or 13 weeks of daily gavage treatment with riddelliine, no increases in the frequency of micronucleated erythrocytes were noted in the peripheral blood of male or female B6C3F1 mice. Use of a single intraperitoneal injection protocol, however, produced a small but significant increase in the frequency of micronucleated eryth-rocytes in peripheral blood of male Swiss mice 48 hours after injection; bone marrow analysis 24 hours after injection demonstrated a small but insignificant increase in the frequency of micronuclei. Unscheduled DNA synthesis was detected in cultured hepatocytes from male and female rats and mice following 5 or 30 days of riddelliine treatment by gavage. In addition, an S-phase DNA synthesis was observed in cultured hepatocytes of male and female rats treated for either time period. CONCLUSIONS: Under the conditions of these studies, there was clear evidence of carcinogenic activity of riddelliine in male and female F344/N rats based primarily on increased incidences of hemangiosarcoma in the liver. The increased incidences of hepatocellular adenoma and mononuclear cell leukemia in male and female rats were also considered to be treatment related. There was clear evidence of carcinogenic activity of riddelliine in male B6C3F1 mice based on increased incidences of hemangiosarcoma in the liver. There was clear evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. Administration of riddelliine by gavage resulted in nonneoplastic lesions in the liver and kidney of male and female rats; the liver and kidney of male and female mice; and the lung and arteries (multiple tissues) of female mice. Decreased incidences of hepatocellular neoplasms in male and female mice were related to riddelliine administration.

Adenoma, Liver Cell↗

PubMed2003

NTP toxicology and carcinogensis Studies of 2,4-hexadienal (89% trans,trans isomer, CAS No. 142-83-6; 11% cis,trans isomer) (Gavage Studies).

UNLABELLED: 2,4-Hexadienal, a colorless to yellow liquid with a pungent "green" or citrus odor, is used as a food additive for flavor enhancement, as a fragrance agent, as a starting material or intermediate in synthetic reactions in the chemical and pharmaceutical industries, as a fumigant, and as a corrosion inhibitor for steel. 2,4-Hexadienal was nominated for study by the National Cancer Institute because of the potential for carcinogenicity based on its alpha,beta-unsaturated aldehyde structure and the potential link between exposure to lipid peroxidation products in the diet and human malignancies. The commercial product is a mixture containing chiefly trans,trans-2,4-hexadienal in equilibrium with cis,trans-2,4-hexadienal. Male and female F344/N rats and B6C3F1 mice received 2,4-hexadienal (89% trans,trans; 11% cis,trans) in corn oil by gavage for 16 days, 14 weeks, or 2 years. Tissues and plasma from dosed rats were examined for malondialdehyde and glutathione concentrations, and DNA adducts were characterized in liver and forestomach samples from dosed rats and mice. Genetic toxicology studies were conducted in Salmonella typhimurium, rat and mouse bone marrow cells, and mouse peripheral blood erythrocytes. 16-DAY STUDY IN RATS: Groups of five male and five female rats were administered 0, 3, 9, 27, 80, or 240 mg 2,4-hexadienal/kg body weight in corn oil by gavage, 5 days per week, for 16 days. Three male and three female 240 mg/kg rats died before the end of the study. Mean body weight gains of 240 mg/kg rats were significantly less than those of the vehicle controls. Clinical findings included diarrhea, ataxia, lethargy, and nasal/eye discharge in males, and lethargy, paleness, and abnormal breathing in females in the 240 mg/kg groups. Liver weights of 240 mg/kg females were significantly greater than those of the vehicle controls. Gross and microscopic lesions indicative of forestomach necrosis and ulceration were present in most 240 mg/kg rats, and forestomach epithelial hyperplasia was microscopically evident in most 80 mg/kg rats. 16-DAY STUDY IN MICE: Groups of five male and five female mice were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 3, 9, 27, 80, or 240 mg/kg, 5 days per week, for 16 days. Chemical-related deaths occurred in one male and one female in the 240 mg/kg groups. Female mice in the 240 mg/kg group lost weight during the study. Gross and microscopic lesions indicative of forestomach necrosis and ulceration were present in all 240 mg/kg mice, and forestomach epithelial hyperplasia and hyperkeratosis were microscopically evident in 80 mg/kg mice. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 7.5, 15, 30, 60, or 120 mg/kg, 5 days per week, for 14 weeks. All rats survived to the end of the study. Mean body weights of 30, 60, and 120 mg/kg males were significantly less than those of the vehicle controls. The only clinical finding attributed to 2,4-hexadienal administration was hypersalivation in 30 and 120 mg/kg males and females. The incidences of forestomach hyperplasia and nasal olfactory atrophy or necrosis were significantly increased in 120 mg/kg rats. Nasal lesions occurred in most 120 mg/kg male rats. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 7.5, 15, 30, 60, or 120 mg/kg, 5 days per week, for 14 weeks. No deaths were attributed to administration of 2,4-hexadienal. Mean body weights of males and females were similar to those of the vehicle controls throughout the study. Clinical findings included salivation and anal wetness in males and females. Kidney weights of 60 and 120 mg/kg males and liver weights of 60 mg/kg males and females were significantly greater than those of the vehicle controls. The incidences of forestomach hyperplasia and/or nasal olfactory atrophy or necrosis were significantly increased in 120 mg/kg mice. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 2,4-hexministered 2,4-hexadienal in corn oil by gavage at doses of 0, 22.5, 45, or 90 mg/kg, 5 days per week, for up to 105 weeks. Survival of all dosed groups of rats was similar to that of the vehicle control groups. The mean body weights of 90 mg/kg males were generally less than those of the vehicle controls throughout the study. The incidences of squamous cell papilloma of the forestomach occurred with positive trends in male and female rats. This neoplasm was found in 58% of males and 34% of females in the 90 mg/kg groups. In the forestomach of male rats, papilloma multiplicity was increased in the 90 mg/kg group, and squamous cell carcinomas were found in one 45 mg/kg male and two 90 mg/kg males. Epithelial hyperplasia of the forestomach occurred in most 45 and 90 mg/kg rats. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 30, 60, or 120 mg/kg, 5 days per week, for up to 105 weeks. Survival of dosed mice was similar to that of the vehicle controls. The mean body weights of all dosed groups were generally similar to those of the vehicle controls throughout the study. The incidences of squamous cell papilloma of the forestomach occurred with positive trends in male and female mice; squamous cell carcinomas were present in 120 mg/kg males and females. Epithelial hyperplasia of the forestomach occurred in many 120 mg/kg mice. Two 120 mg/kg males had uncommon squamous cell carcinoma of the oral cavity (tongue). GENETIC TOXICOLOGY: 2,4-Hexadienal was mutagenic in S. typhimurium strain TA100 with and without induced hamster or rat liver enzymes; no mutagenic activity was detected with strains TA1535 or TA98, with or without S9. Results of bone marrow tests in male rats and male mice given intraperitoneal injections of 2,4-hexadienal showed a small increase in the induction of micronucleated erythrocytes. However, neither test was repeated, and the test results were judged to be inconclusive. Results of peripheral blood micronucleus tests in male and female mice treated with 2,4-hexadienal by gavage for 14 weeks were negative. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was clear evidence of carcinogenic activity* of 2,4-hexadienal in male and female F344/N rats and male and female B6C3F1 mice based on increased incidences of squamous cell neoplasms of the forestomach. The occurrence of squamous cell carcinoma of the oral cavity (tongue) in male B6C3F1 mice may have been related to the administration of 2,4-hexadienal. Hyperplasia of the forestomach in male and female rats and mice was associated with administration of 2,4-hexadienal. Synonyms: Hexa-2,4-dienal; 2,4-hexadienal; 2,4-hexadien-1-al; 2,4-Hx; 1,3-pentadiene-1-carboxaldehyde; 2-propylene acrolein; sorbaldehyde; sorbic aldehyde

Aldehydes↗

PubMed2002

Toxicology and carcinogenesis studies of p-nitrotoluene (CAS no. 99-99-0) in F344/N rats and B6C3F(1) mice (feed studies).

UNLABELLED: p-Nitrotoluene is used to synthesize agricultural and rubber chemicals, azo and sulfur dyes, and dyes for cotton, wool, silk, leather, and paper. p-Nitrotoluene was nominated by the National Institute for Occupational Safety and Health and the NTP for study based on its considerable human exposure as well as the absence of long-term studies of its carcinogenicity in rodents. Male and female F344/N rats and B6C3F1 mice were exposed to p-nitrotoluene (greater than 99% pure) in feed for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, L5178Y mouse lymphoma cells, cultured Chinese hamster ovary cells, and rat and mouse bone marrow cells. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 1,250, 2,500, or 5,000 ppm p-nitrotoluene (equivalent to average daily doses of approximately 55, 110, or 240 mg p-nitrotoluene/kg body weight to males and 60, 125, or 265 mg/kg to females) for 105 or 106 weeks. Survival, Body Weights, and Feed Consumption: Survival of all exposed groups of rats was similar to that of the control groups. Mean body weights of 5,000 ppm male and 2,500 and 5,000 ppm female rats were less than those of the controls during most of the study; mean body weights of 1,250 ppm females were less during the second year of the study. Feed consumption by 5,000 ppm females was less than that by the controls during year 2 of the study. Biomarkers of Exposure: Two urinary metabolites were followed during the study as biomarkers of exposure. The ratios of p-nitrobenzoic acid to creatinine and of p-acetamidobenzoic acid to creatinine determined at 2 weeks and at 3, 12, and 18 months were linearly related to exposure concentration in males and females. Pathology Findings: The incidence of clitoral gland adenoma or carcinoma (combined) was significantly greater in 2,500 ppm females than that in the controls and exceeded the historical control ranges. The incidence of clitoral gland neoplasms was not increased in 5,000 ppm females, possibly because of the lower body weights in this group. The incidences of subcutaneous fibroma and of subcutaneous fibroma or fibrosarcoma (combined) in 2,500 ppm male rats were significantly increased and exceeded the historical control ranges. The incidences of several nonneoplastic kidney lesions were significantly increased in exposed groups of rats, and the severities of these lesions generally increased with increasing exposure concentration. In the spleen, incidences of hematopoietic cell proliferation and pigmentation were significantly increased in the 2,500 and 5,000 ppm groups. Significantly increased incidences of various types of altered cell foci in the liver of males and females were associated with exposure. Incidences of germinal epithelial atrophy of the testis in 5,000 ppm males and endometrial cystic hyperplasia of the uterus in 2,500 and 5,000 ppm females were significantly increased. The incidences of mononuclear cell leukemia were significantly decreased in all exposed groups except 1,250 ppm females. The incidence of interstitial cell adenoma of the testis in 5,000 ppm males was significantly decreased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 1,250, 2,500, or 5,000 ppm p-nitrotoluene (equivalent to average daily doses of approximately 170, 345, or 690 mg/kg to males and 155, 315, or 660 mg/kg to females) for 105 or 106 weeks. Survival, Body Weights, and Feed Consumption: Survival of all exposed groups of male and female mice was similar to that of the control groups. Mean body weights of 5,000 ppm males and females were less than those of the control groups during most of the study. Mean body weights of 2,500 ppm males were less than those of the controls after week 92. Feed consumption by all exposed groups of mice was similar to that by the control groups. Pathology Findings: The incidence of alveolar/bronchiolar adenoma or carcinoma (combined) was significantly greater in 5,000 ppm male mice than in the controls, as was the incidence of alveolar epithelial hyperplasia in this group. The incidences of alveolar epithelial bronchiolization were significantly increased in all exposed groups of males and females. GENETIC TOXICOLOGY: p-Nitrotoluene was not mutagenic in any of several strains of S. typhimurium, with or without metabolic activation enzymes (S9). A positive response to p-nitrotoluene was observed in the L5178Y mouse lymphoma cell assay in trials with S9. Significantly increased sister chromatid exchange frequencies were observed in cultured Chinese hamster ovary cells treated with p-nitrotoluene with and without S9. Chromosomal aberrations were also induced in Chinese hamster ovary cells treated with p-nitrotoluene in the presence of S9; no increased aberrations were seen without S9. p-Nitrotoluene did not induce a significant reproducible increase in the frequency of micronuclei in bone marrow polychromatic erythrocytes of male rats or male mice when administered by intraperitoneal injection. CONCLUSIONS: Under the conditions of these 2-year feed studies there was equivocal evidence of carcinogenic activity* of p-nitrotoluene in male F344/N rats based on increased incidences of subcutaneous skin neoplasms. There was some evidence of carcinogenic activity of p-nitrotoluene in female F344/N rats based on increased incidences of clitoral gland neoplasms. There was equivocal evidence those of the control groups during most of the study. Mean body weights of 2,500 ppm males were less than those of the controls after week 92. Feed consumption by all exposed groups of mice was similar to that by the control groups. Pathology Findings: The incidence of alveolar/bronchiolar adenoma or carcinoma (combined) was significantly greater in 5,000 ppm male mice than in the controls, as was the incidence of alveolar epithelial hyperplasia in this group. The incidences of alveolar epithelial bronchiolization were significantly increased in all exposed groups of males and females. GENETIC TOXICOLOGY: p-Nitrotoluene was not mutagenic in any of several strains of S. typhimurium, with or without metabolic activation enzymes (S9). A positive response to p-nitrotoluene was observed in the L5178Y mouse lymphoma cell assay in trials with S9. Significantly increased sister chromatid exchange frequencies were observed in cultured Chinese hamster ovary cells treated with p-nitrotoluene with and without S9. Chromosomal aberrations were also induced in Chinese hamster ovary cells treated with p-nitrotoluene in the presence of S9; no increased aberrations were seen without S9. p-Nitrotoluene did not induce a significant reproducible increase in the frequency of micronuclei in bone marrow polychromatic erythrocytes of male rats or male mice when administered by intraperitoneal injection. CONCLUSIONS: Under the conditions of these 2-year feed studies there was equivocal evidence of carcinogenic activity of p-nitrotoluene in male F344/N rats based on increased incidences of subcutaneous skin neoplasms. There was some evidence of carcinogenic activity of p-nitrotoluene in female F344/N rats based on increased incidences of clitoral gland neoplasms. There was equivocal evidence in male and female rats, testis in male rats, and lung in male and female mice. Decreased incidences of mononuclear cell leukemia in male and female rats and testicular interstitial cell adenoma in male rats were attributed to exposure to p-nitrotoluene.

Administration, Oral↗

PubMed2002

NTP Technical Report on the metabolism, toxicity and predicted carcinogenicity of diazoaminobenzene (CAS No. 136-35-6).

Diazoaminobenzene is used as an intermediate, complexing agent, and polymer additive. It is also an impurity in certain color additives used in cosmetics, food products, and pharmaceuticals. Diazoaminobenzene was selected for metabolism and toxicity studies based on the potential for worker exposure from its use in laboratories, positive Salmonella typhimurium gene mutation data, its presence as an impurity in foods and cosmetics, and the lack of adequate toxicity data. Several structural analogues and presumed metabolites of diazoaminobenzene are carcinogenic, providing evidence for the possible carcinogenicity of diazoaminobenzene. The chemical structure of diazoaminobenzene suggested that it would be metabolized into aniline and benzene; therefore, metabolism and disposition studies were performed in male and female F344/N rats and male B6C3F1 mice administered a single oral, dermal, or intravenous dose of diazoaminobenzene. Electron spin resonance (ESR) studies were conducted to assess the possible formation of a phenyl radical from the reduction of diazoaminobenzene by components of the cytochrome P450 mixed-function oxidase (P450) system in microsomes or by gut microflora in anaerobic cecal incubations. Bile duct-cannulated male F344/N rats were administered diazoaminobenzene and 5,5-dimethyl-1- pyrroline-N-oxide (DMPO) for in vivo determination of the DMPO-phenyl radical. 16-Day toxicity studies were performed to identify target organs of diazoaminobenzene following dermal application to male and female F344/N rats and B6C3F1 mice. In the disposition and metabolism studies, oral doses of 20 mg/kg to male and female rats and male mice were readily absorbed and excreted mainly in the urine, with exhalation of volatile organics accounting for about 1% of the dose. The only volatile metabolite detected in the breath was benzene, and all the metabolites in the urine were those previously shown to result from the metabolism of benzene and aniline in rats and mice. While dermal doses to rats and mice (2 and 20 mg/cm2) were only slightly absorbed, benzene and aniline metabolites were nonetheless detected in the urine. High circulating levels of benzene, aniline, and their metabolites were detected in the blood of rats administered 20 mg/kg diazoaminobenzene as early as 15 minutes after exposure. At 24 hours after dosing, diazoaminobenzene was detected at low levels (<1%) in the adipose tissue, blood, kidney, liver, muscle, skin, and spleen. Metabolites of benzene and aniline were also formed in an in vitro study using human liver slices. In the ESR spin-trapping experiments, the ESR spectrum of the DMPO-phenyl radical was detected when diazoaminobenzene was incubated with microsomes or P450 reductase, DMPO, and NADPH, or when incubated with cecal contents and DMPO. The DMPO-phenyl radical spectrum was not attenuated by the P450 inhibitor, 1-aminobenzotriazole, or carbon monoxide suggesting that P450s were not required. In in vivo experiments in which rats were administered diazoaminobenzene and DMPO, the DMPO-phenyl radical adduct was detected in bile within 1 hour after treatment. In the 16-day toxicity studies, groups of five male and five female F344/N rats and B6C3F1 mice received dermal applications of 0, 12.5, 25, 50, 100, or 200 mg diazoaminobenzene/kg body weight. Animals were evaluated for absolute and relative organ weights, for hematological effects, and for gross and microscopic lesions. No mortality occurred in rats. However, most male mice exposed to concentrations of 50 mg/kg or greater and female mice exposed to 200 mg/kg died. Body weights of male and female rats and female mice were less than those of the vehicle controls. Similar chemical-related toxicities were observed in both species. Clinical pathology data indicated a chemical-related methemoglobinemia and Heinz body formation in male and female rats and mice. Analysis of organ weights indicated possible chemical-related effects in the thymus, heart, spleen, kidney, and liver of rats and/or mice. Increases in the incidences of several skin lesionseral skin lesions, including hyperplasia of the epidermis and hair follicles, and inflammation in rats and mice and ulceration in female mice were observed. Other nonneoplastic lesions that were considered to be related to diazoaminobenzene administration were atrophy of the thymus, mandibular and/or mesenteric lymph nodes, and white pulp of the spleen, as well as splenic hematopoietic cell proliferation in rats and mice. In mice, there were increased incidences of atrial thrombosis, and necrosis was observed in the renal tubules and liver. Diazoaminobenzene was mutagenic in S. typhimurium strains TA98, TA100, and TA1537 with induced rat or hamster liver S9 enzymes; no activity was noted in strain TA1535, with or without S9. In vivo, two gavage administrations of either diazoaminobenzene or benzene induced highly significant increases in micronucleated polychromatic erythrocytes in bone marrow of male B6C3F1 mice at all doses tested. Diazoaminobenzene is metabolized to the known carcinogens benzene and aniline. Further evidence of this metabolism is that some toxic effects associated with aniline (methemoglobinemia) and benzene (atrophy of the lymphoid tissue) were identified. Based on these results, it is predicted that diazoaminobenzene is a carcinogen.

Animals↗

PubMed2002

NTP toxicology and carcinogensis studies of vanadium pentoxide (CAS No. 1314-62-1) in F344/N rats and B6C3F1 mice (inhalation).

Vanadium pentoxide, commercially the most important compound of vanadium, presents a potential occupational hazard during the cleaning of oil-fired boilers and furnaces, the handling of catalysts, and during the refining, processing, or burning of vanadium-rich mineral ores or fossil fuels. Vanadium pentoxide was nominated for study by the National Cancer Institute as a representative of the metals class study. Male and female F344/N rats and B6C3F1 mice were exposed to vanadium pentoxide (99% pure) by inhalation for 16 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood. 16-DAY STUDY IN RATS: Groups of five male and five female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, 4, 8, 16, or 32 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Three males in the 32 mg/m(3) group died before the end of the study. Mean body weights of males and females exposed to 8 mg/m(3) or greater were less than those of the chamber controls. Clinical findings included rapid respiration and hypoactivity in rats exposed to 16 or 32 mg/m(3). Relative lung weights of 4 mg/m(3) or greater males and 2 mg/m(3) or greater females were significantly greater than those of the chamber controls. Lavage fluid analysis indicated an inflammatory response in the lung that was either directly mediated by vanadium pentoxide or was secondary to lung damage induced by vanadium pentoxide exposure. 16-DAY STUDY IN MICE: Groups of five male and five female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, 4, 8, 16, or 32 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. All males exposed to 32 mg/m(3) and one 8 mg/m(3) male died or were killed moribund before the end of the study. Mean body weights of 16 mg/m(3) males and 8 mg/m(3) or greater females were significantly less than those of the chamber controls, and the 32 mg/m(3) females lost weight during the study. Absolute and relative lung weights of 4 mg/m(3) or greater males and all exposed groups of females and liver weights of 16 mg/m(3) males were significantly greater than those of the chamber controls. The mediastinal lymph nodes were enlarged in 4, 8, and 16 mg/m(3) males and females, and lymphoid hyperplasia was confirmed histologically. Lavage fluid analysis indicated an inflammatory response in the lung that was either directly mediated by vanadium pentoxide or was secondary to lung damage induced by vanadium pentoxide exposure. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, 4, 8, or 16 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 3 months. Seven males and three females exposed to 16 mg/m(3) died during the study. Mean body weights were significantly less in males exposed to 4 mg/m(3) or greater and in females exposed to 16 mg/m(3). Abnormal breathing, thinness, lethargy, abnormal posture, and ruffled fur were observed in rats exposed to 16 mg/m(3). Hematology results indicated that exposure of rats to vanadium pentoxide induced a microcytic erythrocytosis in males and females. Absolute and relative lung weights were significantly greater for 4 mg/m(3) or greater males and females than for the chamber controls as were the relative lung weights of 2 mg/m(3) males. The estrous cycle of females exposed to 8 mg/m(3) was significantly longer than that of the chamber control group, and the number of cycling females in the 16 mg/m(3) group was reduced. The incidences of several nonneoplastic lesions of the lung and nose were significantly increased in males and females exposed to 2 mg/m(3) or greater. Data from pulmonary function analyses indicated that a restrictive lung disease was present in male and female rats exposed to 4 mg/m(3) or greater, while an obstructive lung disease was present only in the 16 mg/m(3) groups. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, 4, 8, or 16 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 3 months. One male exposed to 16 mg/m(3) died before the end of the study. Mean body weights of 8 and 16 mg/m(3) males and 4 mg/m(3) or greater females were significantly less than those of the chamber controls. Absolute and relative lung weights of males and females exposed to 4 mg/m(3) or greater were significantly greater than those of the chamber controls. The epididymal spermatozoal motility of males exposed to 8 or 16 mg/m(3) was significantly decreased. Some mice exposed to 2 or 4 mg/m(3) had inflammation of the lung, and all mice exposed to 8 or 16 mg/m(3) had inflammation and epithelial hyperplasia of the lung. 16-DAY SPECIAL STUDY IN RATS: Groups of 60 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, or 2 mg/m(3) and groups of 40 female rats were exposed to 4 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Alveolar and bronchiolar epithelial hyperplasia was observed in most rats exposed to 2 or 4 mg/m(3) on days 6 and 13. Histiocytic infiltration and inflammation occurred in a time- and concentration-related manner. Cell turnover rates were increased in the terminal bronchioles on days 6 and 13 and in the alveoli in the 4 mg/m(3) group on day 6 and in all exposed groups on day 13. Assessment of lung vanadium concentrations suggested deposition and clearance exhibited linear kinetics over the exposure range studied. Lung clearance half-times ranged from 4.42 to 4.96 days. 16-DAY SPECIAL STUDY IN MICE: Groups of 60 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, or 4 mg/m(3) and groups of 40 female mice were exposed to 8 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Alveolar and bronchiolar epithelial hyperplasia occurred with similar incidences and severities among the exposed groups on days 6 and 13, and time- and concentration-related increases in the incidences of interstitial inflammation and histiocytic infiltration also occurred in these groups. Cell turnover rates were increased in the terminal bronchioles on day 6 and remained greater than those of the chamber controls on day 13. In the alveoli, cell turnover rates were increased in an exposure concentration-related manner on day 13; cell turnover rates were increased only in the 8 mg/m(3) group on day 6. Assessment of lung vanadium concentrations suggested deposition and clearance exhibited linear kinetics over the exposure range studied. Lung clearance half-times ranged from 2.40 to 2.55 days. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 0.5, 1, or 2 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 104 weeks. Survival and body weights of males and females were generally similar to those of the chamber controls. Mean body weights of females exposed to 2 mg/m(3) were less than those of the chamber controls throughout the study. Alveolar/bronchiolar neoplasms were present in exposed groups of male rats, and the incidences often exceeded the historical control ranges. Alveolar/bronchiolar adenomas were present in 0.5 and 1 mg/m(3) females; one 2 mg/m(3) female also had an alveolar/bronchiolar carcinoma. The incidence of alveolar/bronchiolar adenoma in the 0.5 mg/m(3) group was at the upper end of the historical control ranges. Nonneoplastic lesions related to vanadium pentoxide exposure occurred in the respiratory system (lung, larynx, and nose) of male and female rats, and the severities of these lesions generally increased with increasing exposure concentration. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, or 4 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 104 weeks. Survival of 4 mg/m(3) males was significantly less than that of the chamber controls. Mean body weights of 4 mg/m(3) males and all exposed groups of females were generally less than those of the chamber controls throughout the study, and those of males exposed to 2 mg/m(3) were less from week 85 to the end of the study. Many mice exposed to vanadium pentoxide were thin, and abnormal breathing was observed in some mice, particularly those exposed to 2 or 4 mg/m(3). The incidences of alveolar/bronchiolar neoplasms were significantly increased in all groups of exposed males and females. Nonneoplastic lesions related to vanadium pentoxide exposure occurred in the respiratory system (lung, larynx, and nose) of male and female mice, and the severities of these lesions generally increased with increasing exposure concentration. Bronchial lymph node hyperplasia was present in many exposed females. MOLECULAR ONCOLOGY STUDIES: K-ras codon 12 mutation and loss of heterozygosity on chromosome 6 were detected in vanadium pentoxide-induced alveolar/bronchiolar carcinomas from mice. GENETIC TOXICOLOGY: Vanadium pentoxide was not mutagenic in Salmonella typhimurium strain TA97, TA98, TA100, TA102, or TA1535, with or without induced rat or hamster liver S9 enzymes. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was some evidence of carcinogenic activity of vanadium pentoxide in male F344/N rats and equivocal evidence of carcinogenic activity of vanadium pentoxide in female F344/Nrats based on the occurrence of alveolar/bronchiolar neoplasms. There was clear evidence of carcinogenic activity of vanadium pentoxide in male and female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. (ABSTRACT TRUNCATED)

Animals↗

PubMed2002