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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↗
PubMed1980

Bioassay of a Mixture of 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin and 1,2,3,7,8,9-Hexachlorodibenzo-p-dioxin (Dermal Study) for Possible Carcinogenicity (CAS No. 57653-85-7; CAS No. 19408-74-3).

Hexachlorodibenzo-p-dioxin (HCDD) is formed as a byproduct during the manufacture of certain chlorophenols and has been found in trichlorophenol, tetrachlorophenol, pentachlorophenol and in the chlorophenol-derived herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). From 1967 to 1970, the concentration of HCDD in commercial pentachlorophenol ranged from 0.03 to 38 ppm. Since then, HCDD levels in pentachlorophenol have been reduced to less than 1 ppm. A bioassay of a mixture of 1,2,3,6,7,8-and 1,2,3,7,8,9-hexachlorodibenzo-p-dioxins (HCDD) for possible carcinogenicity was conducted by dermal application of a suspension of this substance to Swiss-Webster mice. HCDD (0.01 &mgr;g) suspended in 0.1 ml acetone was applied to the backs of 30 mice of each sex 3 days per week for 104 weeks. During the first 16 weeks, doses were 0.005 &mgr;g HCDD per application. An additional 30 mice of each sex were pretreated with one application of 50 &mgr;g DMBA in 0.1 ml acetone 1 week before the initiation of the HCDD applications. As vehicle controls, 45 mice of each sex received 0.1 ml of acetone three times per week. Thirty animals of each sex served as untreated controls. Mean body weights of all test and vehicle control mice were comparable throughout the bioassay; mean body weights of untreated controls were higher than those of the test and vehicle-control groups. In male mice, the incidence of alveolar/bronchiolar carcinomas in the group administered only HCDD was significantly higher (P=0.045) than that in the vehicle-control group; however, the incidence was not significantly higher when compared with untreated controls. In female mice, the incidences of fibrosarcomas of the skin were significantly higher (P=0.044) in animals administered HCDD (both with and without pretreatment with DBMA) than in the untreated-control group; however, when the incidences were compared with those of the vehicle controls (relative risk=3.037) the results were not significant. Under the conditions of this bioassay, HCDD was not carcinogenic for male or female Swiss-Webster mice. Levels of Evidence of Carcinogenicity: Male Mice: Negative Female Mice: Negative Synonym: HCDD

Journal Article↗
PubMed1980

Bioassay of a Mixture of 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin and 1,2,3,7,8,9-Hexachlorodibenzo-p-dioxin (Gavage) for Possible Carcinogenicity (CAS No. 57653-85-7,CAS No. 19408-74-3).

Hexachlorodibenzo-p-dioxins (HCDD) are formed during the manufacture of certain chlorophenols. They have been found in trichlorophenol, tetrachlorophenol, and pentachlorophenol and in the chlorophenol-derived herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). From 1967 to 1970, the concentration of HCDD in commercial pentachlorophenol ranged from 0.03 to 38 ppm. Since then, HCDD levels in pentachlorophenol have been less than 1 ppm. A bioassay of a mixture of 1,2,3,6,7,8- and 1,2,3,7,8,9-hexachlorodibenzo-p-dioxin (HCDD) for possible carcinogenicity was conducted by administering the test material by gavage to Osborne-Mendel rats and B6C3F1 mice for 104 weeks. Fifty rats and 50 mice of each sex were administered HCDD suspended in a vehicle of 9:1 corn oil-acetate 2 days per week for 104 weeks at doses of 1.25, 2.5, or 5 &mgr;g/kg/wk for rats and male mice and 2.5, 5, or 10 &mgr;g/kg/wk for female mice. Seventy-five rats and 75 mice of each sex served as vehicle controls. In addition, one untreated control group containing 25 rats and 25 mice of each sex was present in the HCDD treatment room, and one untreated control group containing 25 rats and 25 mice of each sex was present in the vehicle control room. All surviving animals were killed at 105 to 108 weeks. In rats, a dose-related depression in mean body weight gain became evident in the males after week 68 of the bioassay and in the females after week 33. In mice, the mean body weight gain in the dosed groups was comparable with that of the vehicle control groups. No other toxic clinical signs were reported in either the rats or the mice. Administration of HCDD had no adverse effect on the survival of either species. In male rats, hepatocellular carcinomas or neoplastic nodules occurred at low incidences that were dose related (P=0.003). In a direct comparison, the incidence of these tumors in the high-dose group was higher (P=0.022) than that in the corresponding vehicle-control groups, but the Bonferroni requirement of P=0.017 for the multiple comparison of three dosed groups with a control group was not met. In female rats, hepatocellular carcinomas, adenomas, or neoplastic nodules occurred at incidences that were dose related (P<0.001), and in direct comparisons the incidences of these tumors in the mid-and high-dosed groups were significantly higher (P=0.006 and P<0.001, respectively) than those in the corresponding vehicle-control group. In male mice, hepatocellular carcinomas or adenomas occurred at incidences that were dose related (P=0.001), and in a direct comparison the incidence of these tumors in the high-dose group was significantly higher (P=0.001) than that in the corresponding vehicle-control group. In female mice, hepatocellular carcinomas or adenomas occurred at incidences that were dose-related (P=0.002), and the incidence of these tumors in the high-dose group was significantly higher (P=0.004) than that in the corresponding vehicle-control group. Complex nonneoplastic toxic liver lesions were seen in all dosed groups of rats and mice. Compound-associated hyperplastic lesions of the lung were also found in both male and female rats. Under the conditions of this bioassay, HCDD administered by gavage was carcinogenic, causing increased incidences of hepatocellular carcinomas or neoplastic nodules in female Osborne-Mendel rats and inducing hepatocellular carcinomas and adenomas in male and female B6C3F1 mice. HCDD was not demonstrated to be carcinogenic for male rats. Levels of Evidence of Carcinogenicity: Male Rats: Equivocal Female Rats: Positive Male Mice: Positive Female Mice: Positive Synonym: HCDD

Journal Article↗
PubMed1986

Functional derangement of liver mitochondria from hexachlorobenzene-treated rats.

This study investigated impairment of oxidative phosphorylation in mitochondria isolated from the liver of hexachlorobenzene (HCB)-treated rats. Partial and reversible uncoupling of the phosphorylative process was found in liver mitochondria from rats dosed with HCB for 60 days. Pentachlorophenol, endogenously formed by HCB metabolism, was detected in the mitochondria at a concentration of 0.3-0.4 nmol/mg protein. Based on the effect of pentachlorophenol, added in vitro at a concentration similar to that found in vivo, it was concluded that the uncoupling of oxidative phosphorylation under these experimental conditions was almost completely due to the presence of pentachlorophenol.

Animals↗
PubMed1994

[Chlorophenols in urine as an environmental medicine monitoring parameter].

Chlorophenols occur ubiquitously in the environment. They are taken up as such in man or are formed in intermediary metabolism e.g. from chlorobenzenes. In particular pentachlorophenol (PCP) is one of those chemical substances used up to the early 70's as a component of wood preservatives also indoors; for many years it has been at the centre of discussion about the environment. Mono, di, tri and tetrachlorophenols as well as pentachlorophenol occur in the urine in the general population often in surprisingly high concentrations. An increased chlorophenol excretion under certain circumstances also indicates an increased dioxin exposure (pre-dioxins). Possible sources of emission and routes of absorption for corresponding organochlorine compounds can be found in industry, agriculture and also private households. Environmental analysis in the air, in earth or dust do not allow any evaluation of health risks. Only biological monitoring with qualitative and quantitative determination of the actual concentration of the substance taken up by the organism allows a reliable estimation of the individual health risk. The background exposure of the general population not occupationally exposed to organochlorine compounds can be used for the determination of so-called norm values. For the determination of the chlorophenol spectrum 50 ml urine are necessary. The following values can be given as reference values for the most important chlorophenols: 4-monochlorophenol: 7.5 micrograms/l, 2.4-dichlorophenol and 2.5-dichlorophenol: 33.6 micrograms/l, 2.4.6-trichlorophenol: 4.7 micrograms/l, 2.4.5-trichlorophenol: 4.5 micrograms/l, 2.3.4.6-tetrachlorophenol and 2.3.5.6-tetrachlorophenol: 22.0 micrograms/l, pentachlorophenol 9.0 micrograms/l urine.

Chlorophenols↗
PubMed1996

Hierarchical cluster analysis of environmental pollutants through P450 induction in cultured hepatic cells.

Environmental pollutants are classically associated with increased drug metabolism. Cultures of rat hepatocytes, quail hepatocytes, and human hepatoma (Hep G2) cells were used to study the effects of pesticides on drug-metabolizing enzymes. Membrane integrity and mitochondrial activity were evaluated and induction of ethoxycoumarin-O-deethylase and ethoxyresorufin-O-deethylase activities were measured. Induced P450s were identified by immunoblotting. Pentachlorophenol and lindane appeared as the strongest inducers. On the immunoblots, specific antibodies revealed induced CYP1A1 in fetal rat hepatocytes, CYP2B in quail hepatocytes, and CYP3A7 in Hep G2 cells. Pesticide effects on these different activities in each type of cultured cells were compared by cluster analysis. Results obtained under similar conditions with reference inducers phenobarbital (PB) and benzo[a]anthracene and other environmental pollutants (polychlorobiphenyls) were added to previous data prior to multivariate analysis. The tested products fell into four major groups: a first group with pentachlorophenol, identified as a CYP3A inducer; a second group containing the methylcholanthrene-type inducers that increase CYP1A-related activities; a third class represented by dieldrin, a PB-type inducer; a fourth group including inert compounds or weak inducers. Lindane shares the criteria of the second and third groups and seems to induce both CYP1A and CYP2B activities. The current study results highlight the advantage of using several types of cultured hepatocytes to evaluate the short-term toxicity of environmental pollutants in vitro and constitute a useful model for predicting the potential toxicity of pesticides in humans (Hep G2 cells) and wildlife (fetal quail hepatocytes).

7-Alkoxycoumarin O-Dealkylase↗
PubMed2000

Shake-flask test for determination of biodegradation rates of (14)C-labeled chemicals at low concentrations in surface water systems.

A simple shake-flask surface water biodegradability die away test with (14)C-labeled chemicals added to microgram per liter concentrations (usually 1-100 microg/L) is described and evaluated. The aim was to provide information on biodegradation behavior and kinetic rates at environmental (low) concentrations in surface water systems. The basic principle of measurement was to determine evolved CO(2) indirectly from measurements of total organic activity in subsamples after stripping off their content of CO(2). Used with surface water alone the test simulates a pelagic environment and amended with sediments (0.1-1 dry weight/L) the test is intended to simulate a water environment with suspended solids (e.g., resuspended sediments). A protocol of the test used with the (14)C technique or with specific chemical analysis was recently developed by the International Organization for Standardization. Practical experience with the method is presented for a set of reference substances. These substances could be ranked in five groups of decreasing biodegradability: aniline>p-nitrophenol, 2, 4-dichlorophenoxyacetic acid>4-chloroaniline>maleic hydrazide, pentachlorophenol>atrazine. It was found that degradation rates and lag periods varied considerably among sampling sites and sometimes also among samples from the same site. No significant correlation could be established between degradation rates and microbial biomass estimates. Even small portions of added sediments greatly enhanced biodegradation of the absorbable compound pentachlorophenol, probably by providing sites for microbial attachment. Repeated tests indicated consistent degradation behavior for the readily degradable substances, whereas degradation sometimes stopped or failed with the more recalcitrant substances. A preadaptation step involving regular reinoculation with freshly collected surface water could, however, overcome the problems of false-negative results.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2002

Responses of microbial activity and decomposer organisms to contamination in microcosms containing coniferous forest soil.

Soil respiration from microcosms contaminated with pentachlorophenol, 2-ethanolhexanoate, creosote, CuSO4, and benomyl was measured in order to evaluate usefulness of soil microcosms and microbial respiration rate monitoring as a toxicity test in soils with high organic matter content. Coniferous forest soil and its organisms were used as test objects. In addition, how a short-term low temperature period including frost affects respiration dynamics in stressed soils was studied, i.e., whether contaminants reduce resistance of the community to other (also natural) stresses. In addition, at the end of the experiment, effects of contaminants on faunal and microbial community structures were analyzed. Soil respiration measurements from the microcosms appeared to be a sensitive parameter for testing community-level effects of chemicals in the soil with high organic matter content. An 84-day exposure had acute effects, long-term effects, delaying effects, and total recovery of community respiration. Direct negative and indirect positive effects of chemical contamination on the community of soil organisms were found. Responses to contamination of soil respiration rate and structure of the soil community were parallel. Addition of pentachlorophenol, 2-ethanolhexane, and Cu into the soil reduced frost resistance of the decomposer community. It was concluded that soil respiration monitoring of artificially contaminated soil microcosms seems to be a useful tool for testing community-level toxic effects of chemicals.

Antidotes↗
PubMed1983

Electrical conductivity, transfer of hydrogen ions in lipid bilayer membranes and uncoupling effect induced by pentachlorobenzenethiol (pentachlorothiophenol).

Pentachlorobenzenethiol (PCBT) has been considered an anomalous uncoupler. It was reported as active in mitochondria, but not effective in inducing electrical conductivity in lipid bilayer membranes. We have overcome the experimental difficulties associated with accurate determination of the induced conductivity. The main contributing factors to the difficulties, we discovered, are the photolability and the low solubility of the compound in aqueous medium. We have conclusively demonstrated that PCBT does induce conductivity in lipid bilayers and compared this conductance with its uncoupling activity reported by other investigators in the literature. We present the results of steady-state current-voltage measurements: conductance dependence on applied voltage for various values of pH, buffer strength and PCBT concentration, as well as the dependence of the conductance on pH, buffer strength and PCBT concentration in the limit of zero applied voltage. We have also compared the above results with those obtained previously with pentachlorophenol. Our experimental results on PCBT-induced membrane conductance suggest that PCBT belongs to class II uncouplers and that "disulfide dimer" of PCBT is membrane inactive. Thus the replacement of oxygen in molecular structure of pentachlorophenol (R-OH) by sulfur (R-SH) does not change the protonophoretic activity of the compound. The conductivity of a membrane is due to PCBT-induced hydrogen ion transfer and it was found to be limited by the kinetics of reactions coupled to transmembrane charge transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol↗
PubMed1982

Differential effects of environmental chemicals on liposomal bilayers. Fluorescence polarization and pesticide-lipid association studies.

The thermal dependence of the fluorescence polarization of 1,6-diphenylhexatriene was recorded upon interaction of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and some other pesticides with dipalmitoylphosphatidylcholine liposomes. Differential effects on the gel-crystalline phase were observed. Most substances decreased probe polarization; pentachlorophenol caused an increase of this parameter. The DDT-induced change of polarization was also dependent on the vesicle concentration thus indicating the influence of light scattering. The amount of DDT and pentachlorophenol residing in the lipid bilayer was determined to confirm the localization in the membrane. Correlation with the effects on probe polarization was obtained. The difference in response of the fluorescent probe to the presence of foreign molecules in the lipid bilayer may reflect different modes of interaction.

DDT↗
PubMed1988

The effect of iron overload on the mitochondrial porphyrin level in the hexachlorobenzene induced experimental porphyria.

Liver mitochondria isolated from rats treated with hexachlorobenzene plus iron, present a lower content of total porphyrin in respect to that of mitochondria from rats fed hexachlorobenzene alone. The in vitro mitochondrial porphyrin accumulation processes have been studied in mitochondria from iron loaded rats. It has been found that under these conditions the active porphyrin uptake process, which is driven by the K+ transmembrane gradient, is maximally inhibited in the presence of pentachlorophenol at a concentration similar to that found in vivo in the hexachlorobenzene experimental porphyria. By contrast the same degree of inhibition is presented by control mitochondria only in the presence of pentachlorophenol plus valinomycin, a condition which collapses the transmembrane K+ gradient. A strict correlation between porphyrin uptake and K+ concentration has been found in control as well as in iron treated mitochondria. A possible involvement of peroxidative reactions in the mitochondrial membranes has been proposed as a cause of the changes in the permeability properties of the mitochondrial membranes in the experimental chronic hepatic porphyria under conditions of iron overload.

Animals↗
PubMed1982

Sex differences in the metabolism of hexachlorobenzene by rats and the development of porphyria in females.

Male and female F 344 rats were dosed every other day for 103 days with 50 mumole of hexachlorobenzene (HCB)/kg. Females developed a hepatic porphyria, the urine and liver levels of porphyrins being 40- and 310-fold higher respectively than those of males. Urine was periodically hydrolysed and analysed for the three metabolites pentachlorophenol, 2,3,5,6-tetrachlorobenzene-1,4-diol and pentachlorothiophenol (derived from the mercapturate). The combined urinary excretion of these was greater in females than males, especially during the first 10 weeks. Pentachlorothiophenol was particularly high in female urine. After 103 days this metabolite was slightly less in female faeces than in male's but free hepatic pentachlorothiophenol was 3.6-fold greater. Although total 24 hr excretions of metabolites were higher by females than males and after 7 daily doses of HCB, a difference in this respect was not conclusively proven. However, total pentachlorothiophenol excretion was always significantly greater by females. The male/female ratios for pentachlorophenol and pentachlorothiophenol in bile were identical to those for faeces. Excretion of metabolites by both adult males and females was stimulated by pretreatment with diethylstilboestrol (DES). No sex differences in metabolism were observed with immature rats.

Animals↗
PubMed1993

Cytochrome d induction in Escherichia coli growing under unfavorable conditions.

Growth of E. coli in the presence of the protonophorous uncoupler pentachlorophenol is shown to strongly enhance levels of cytochrome d, a putative Na(+)-motive oxidase. This effect was found to be arrested by chloramphenicol and stimulated by high Na+ concentration in the growth medium. The induction of cytochrome d takes place in a mutant deficient in the F0F1 ATP-synthase but does not occur in mutants deficient in either of two different components of the Arc system. Similar relationships were revealed when pentachlorophenol was replaced by ferricyanide and phenazine methosulfate, agents oxidizing the respiratory chain. Induction of cytochrome d is also shown to occur in riboflavin-deficient mutants growing in the presence of such low riboflavin concentrations as to be insufficient to maintain a high respiration rate. It is suggested (i) that it is delta mu H+ decrease rather than reduction of the respiratory chain that is the signal for the induction of cytochrome d, and (ii) the Arc system is involved in this type of metabolic regulation.

Chloramphenicol↗
PubMed1994

Nematode test to estimate the hazard potential of solved contaminations.

The acute toxicity of lindane, pentachlorophenol and a fluortenside was examined using a recently developed ecotoxicity test with the terrestrial nematode species Panagrellus redivivus. The exposure was performed in aqueous solution over an investigation period of 96 h. For lindane a time dependent decrease of the survival rate (LC50 after 96 h: 0.4 mg/l) was observed which indicates a high cuticular permeability of the insecticide. For pentachlorophenol the LC50 (96 h) was 13 mg/l, for the fluortenside a value of 110 mg/l was determined.

Animals↗
PubMed1996

Estimation of kinetic rate constants for biodegradation of chemicals in activated sludge wastewater treatment plants using short term batch experiments and microgram/L range spiked concentrations.

Biodegradation rate constants that are believed to be predictive for activated sludge sewage treatment plants have been determined at microgram/L concentration levels using short term (hours) laboratory scale batch experiments with activated sludge. Rate constants were estimated for four model chemicals with widely different biodegradability characteristics, and experiments were conducted with sludges of various origin and treatment. Test substances were applied at concentrations ranging from a few microgram/L for deriving first order rate constants and up to several mg/L for full investigation of the kinetics. Model substances were acetate, aniline, 4-chloroaniline and pentachlorophenol and their biodegradation was assessed by means of 14C tracer technique. Some experiments included test concentrations equal to those prescribed in standard biodegradability tests (20 mg DOC/L). Sludge types investigated included adapted and non-adapted sludge from laboratory scale semicontinuous reactors as well as sludges collected from a pilot scale sewage treatment plant loaded with predominantly domestic sewage. At low chemical concentrations ( < approx. 100 micrograms/L) first order degradation rate constants were reasonably constant and varied only little with the applied concentration. With aniline, however, elimination rates increased at concentrations below about 20 micrograms/L, probably because transient sorption became significant. At higher concentrations absolute (linear) degradation rates could be described by saturation kinetics, and for aniline a half saturation constant, K(S), was estimated at 3 mg/L. "Best estimates" of average first order rate constants in the low concentration regime measured with 3 g SS/L and at 22 degrees C were: acetate, 8 h-1; aniline, 0.8 h-1, 4-chloroaniline, 0.15 h-1, and pentachlorophenol, 0.01 h-1 (non adapted sludge) or 0.02 h-1 (adapted sludge). These figures seem to agree well with standard or default biodegradation rate constants for sewage treatment plants suggested in a European Union technical guidance document for chemical risk assessment, which is currently under preparation.

Acetates↗
PubMed1982

A laboratory method for testing the volatility from aqueous solution: first results and comparison with theory.

The mobility of a chemical in the environment is often determined by its volatilization from aqueous solution, especially if it shows poor water solubility and/or high vapor pressure. A small laboratory apparatus is described which allows the simulation of the volatilization process from a stirred water body with well-defined wind velocities and water temperatures. In experiments with naphthalene, pentachlorophenol, trichloroethene, and di(2-ethylhexyl)phthalate, substance concentrations in the water body decrease exponentially, in accordance with theory. Half-residence times are found to be independent of wind velocity (v less than 1 m sec-1) or air humidity, but are strongly dependent on temperature. The measured substance fluxes through the water surface are comparable with theoretical values. In the case of pentachlorophenol, which partly dissociates in aqueous solution, the volatility is controlled by the pH value of the solution.

Diethylhexyl Phthalate↗
PubMed1984

Use of plant cell cultures to study the metabolism of environmental chemicals.

The metabolism of the following environmental chemicals has been studied in cell suspension cultures of wheat (Triticum aestivum L.) and soybean (Glycine max L.):2, 4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), hexachlorobenzene, pentachlorophenol, diethylhexylphthalate , benzo [alpha] pyrene, and DDT. All chemicals tested, including the persistent ones, were partially metabolized. Polar conjugates predominated in all cases. A covalent incorporation into lignin could be demonstrated for 2,4-D and pentachlorophenol. A specific deposition in the cellular vacuole could be demonstrated for the beta-D-glucopyranoside conjugates derived from 2,4-D. A rapid assay procedure to evaluate the metabolism of a given 14C-labeled chemical in plant cell suspension cultures is described. This procedure requires about 1 week, and the reproducibility of the results obtained has been assessed.

Benzo(a)pyrene↗
PubMed1992

Effect of ambient oxygen concentration upon the acute toxicity of chlorophenols and heavy metals to the groundwater copepod Parastenocaris germanica (Crustacea).

Acute static toxicity experiments have been performed under normoxic and hypoxic conditions. The test animals used were adults of the groundwater-adapted copepod Parastenocaris germanica. The animals originated from a sandy, gravelly phreatic aquifer of the Meuse valley in The Netherlands. Toxicants applied were pentachlorophenol, 3,4-dichlorophenol, zinc, and cadmium. The results were statistically evaluated by a log-logistic model. LC50 and LC5 values with 95% confidence limits were calculated. Response models of application under both oxygen conditions were compared. The influence of ambient oxygen concentration on sensitivity appeared to be very small; only in the case of pentachlorophenol were hypoxic and normoxic models slightly but significantly different. Comparisons with the sensitivity of other organisms are made and the results are discussed against the specific physiological adaptations of the organisms to groundwater conditions.

Animals↗