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At least 973 records · Page 54Linked to original sources
PubMed1991

Liver ferrochelatase from normal and hexachlorobenzene porphyric rats. Mechanism of drug action.

1. The action of hexachlorobenzene (HCB) on hepatic ferrochelatase was investigated. 2. A direct action of HCB, pentachlorophenol, porphyrins and haem on this enzyme activity was discarded. 3. In HCB porphyric liver there is probably an activator tightly bound to the enzyme. 4. Pyridoxal phosphate (PPL) may be a cofactor of ferrochelatase from both normal and porphyric rats. 5. The PPL would be involved in the binding site of Fe2+ or at least in the approaching of Fe2+ to the active site of the enzyme. 6. The differences found between normal and porphyric preparations could be attributed to conformational changes elicited by the HCB.

Animals↗
PubMed1995

Induction of 8-hydroxy-2-deoxyguanosine and single-strand breaks in DNA of V79 cells by tetrachloro-p-hydroquinone.

The biocide pentachlorophenol (PCP) is in part metabolized, by microsomal enzymes, to tetrachloro-p-hydroquinone (TCHQ), which easily oxidizes to its semiquinone radical. Redox cycling of this compound produces reactive oxygen species (ROS) which ultimately may damage cellular DNA. Here, we report on DNA damage generated by TCHQ in hamster lung fibroblasts (V79 cells) using 8-hydroxy-2-deoxyguanosine (8-OH-dG) as a marker of a major oxidative genetic lesion and measuring the induction of DNA single-strand breaks (DNA SSB) with the aid of the alkaline elution assay. TCHQ was administered to cell cultures in concentrations of 6.25, 12.5, 25, and 50 microM for 1 h. 6.25 and 12.5 microM had no significant effect on both parameters, whereas the higher concentrations resulted in increases of the level of 8-OH-dG (2.3- and 2.0-fold, respectively) and induced DNA SSB. The latter lesion may arise from (i) direct attack of OH., (ii) repair of hydroxylated DNA bases, or (iii) cytotoxic effects. Metabolic transformation of PCP to TCHQ and/or other metabolites with quinoid structures and the subsequent generation of ROS, producing oxidative DNA damage, may play a role in PCP-induced carcinogenicity observed in mice.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1984

Effects of metals and organic compounds on hepatic glutathione, cysteine, and acid-soluble thiol levels in mullet (Mugil cephalus L.).

The hepatic acid-soluble thiol content of striped mullet (Mugil cephalus) exposed to cadmium (10 mg/liter seawater), mercury (200 micrograms/liter), fluorene (100 micrograms/liter), dibenzofuran (750 micrograms/liter), or a 20% water-soluble fraction of a No. 2 fuel oil, and of winter flounder (Pseudopleuronectes americanus) exposed to pentachlorophenol (200 micrograms/liter) for up to 3 weeks was determined. Exposure to these chemicals caused an elevation of hepatic acid-soluble thiol content over control values. Similarly, the acid-soluble thiol content was 1.75 times control values 24 hr after injection with acetaminophen (40 mg/100 g body wt, ip). In contrast, hepatic acid-soluble thiol concentrations did not fluctuate after feeding or during short-term starvation, or after acute or chronic physical trauma. Thus, the increase in hepatic acid-soluble thiols observed in mullet appears to be a specific response to chemical insult. The effect of chemical exposure on specific thiols can vary with the compound under investigation. Glutathione accounted for most of the acid-soluble thiol increase observed in mullet exposed to oil, whereas other acid-soluble thiols were also elevated after exposure to cadmium. Injection of [14C]glycine into cadmium- and oil-treated mullet showed that hepatic uptake of this amino acid substrate and its incorporation into hepatic glutathione increased after chemical exposure. The proportion of the total [14C]glycine in the liver incorporated into glutathione was unchanged after oil exposure, but was significantly increased in cadmium-exposed fish. These results suggest that chemicals may elevate glutathione content by enhancing the hepatic uptake of amino acid substrates and also the activity of biosynthetic enzymes.

Acetaminophen↗
PubMed1996

Biodegradability simulation studies in semicontinuous activated sludge reactors with low (microgram/L range) and standard (ppm range) chemical concentrations.

The official OECD/EEC activated-sludge biodegradability simulation test has been criticised for providing a poor simulation of the biodegradability behaviour of industrial chemicals in municipal sewage treatment plants due to the high dosed concentration of test substance of approx. 20-40 mg/L necessitated by measuring compound removal by DOC-analysis. Realistic concentrations of industrial chemicals are more commonly in the microgram/L range. With increasing concentration both the kinetic regime of degradation and the adaptation behaviour can be expected to change. Results from a comparative study in semicontinuous reactors with high (20 mg DOC/L) and low (10 micrograms test substance/L) inlet concentrations of aniline, 4-chloroaniline, and pentachlorophenol, conducted by means of 14C-tracer technique, revealed large differences in biodegradation behaviour between the two concentration levels and led to the following tentative general conclusions: 1) the percentage of test compound removed by unadapted sludge tends to be higher with test compound dosed at trace concentrations than at standard (high) concentrations (20 mg/DOC/L); 2) by contrast, in successfully adapted systems, the removal percentage (and the "extent of adaptation") may be largest with high concentrations; 3) the use of real sewage instead of peptone synthetic sewage better safeguards against sludge deterioration, in particular at low sludge retention times, and tends to increase the adaptation potential of the sludge; 4) the use of synthetic sewage in combination with regular reinoculation of the reactor (in this study by replacing 10% of the sludge with freshly collected sludge once a week) may be a feasible alternative to using real sewage.

Aniline Compounds↗
PubMed1985

Effects of various organic chemicals on the regreening of red colored Chlorella zofingiensis.

Under nitrogen-deficient culture conditions Chlorella zofingiensis decomposes the chlorophylls, synthesizes secondary cartenoids, and thus develops red colored resting stages (akinetes). On transfer of the akinetes into nitrogen-containing fresh culture medium the algae regreen completely within a short period. The results of the experiments presented in this study show that the regreening process reacts with high sensitivity to the addition of environmentally hazardous chemicals. This system proved to be much more sensitive than other methods of testing for ecotoxicity. This screening test is universally applicable and offers, in addition, the possibility of testing volatile compounds since it is carried out in air-tight culture vessels. A phytotoxicity of 50% calculated as inhibition of the chlorophyll biosynthesis during exposure for 48 hr was found for paraquat at concentrations of 0.15 microM (added as methysulfate) and 0.28 microM (added as chloride) and for pentachlorophenol (PCP) at 0.16 microM. The chemicals 2- and 4-nitrophenol, however, proved to be much less toxic. Here, a 50% inhibition of chlorophyll biosynthesis was observed at 49 and 75 microM. When exposed to 4-chloroaniline even concentrations of 200 microM were not sufficient to cause a 50% inhibition of the regreening process. In additional experiments the influence of increasing salt concentrations (NaCl stress) and simultaneous exposure to the toxicants was examined. A step-by-step increase in the salinity of the experimental medium resulted in a drastic reduction of the toxicity caused by the addition of paraquat. This effect was much less pronounced when PCP was employed as toxicant. A different result was obtained with 2-nitrophenol: Here the toxic action was slightly enhanced. Differences in the time-dependent toxic response were also observed using the diverse toxicants. Probable causes are discussed.

Aniline Compounds↗
PubMed1986

Comparison of methods to test chemicals for side effects on soil microorganisms.

The effects of the test chemicals pentachlorophenol (PCP) and HgCl2 on the bioactivity of microorganisms in three different soils were studied in low and high concentrations (2 and 20 ppm). Bioactivity was measured in long-term experiments (18 weeks) by a threefold application of chemicals to soils of varying moisture content. The selected tests were measurements of ATP, of heat output under aerobic and anaerobic conditions and after amendment with glucose, of soil respiration after the addition of glucose, and Fe(III) reduction. The suitability of each test depends on soil microorganisms, on environmental conditions, and on soil properties. The effects caused by the chemicals were as follows. For the low concentration, stimulation or inhibition were mostly repaired within the observation period. The high concentration mostly induced inhibitions which increased or decreased as a consequence of the repeated application of the chemicals. The effects of chemicals were strongly modified by the soil types: in a soil with high organic matter content, differences to the control were lower than in soils with lower organic matter content. These experiments also indicate that measurement of only one physiological parameter is not sufficient to characterize chemicals ecotoxicologically.

Carbon Dioxide↗
PubMed1988

Acclimatization of roach, Rutilus rutilus (L.), to toxic components of kraft pulp mill effluents.

Roach (Rutilus rutilus) were exposed, along with their appropriate controls, to a simulated bleached kraft mill effluent (KME-Sa + CP) first for 38 days at a concentration of 0.035 X LC50 and then for 14 days at 0.07 X LC50. During the experiment, their tolerances to KME-Sa + CP were tested five times by measuring the 48-hr LC50 values. In addition, the growth of roach was monitored. At the end of the exposure, accumulation of [14C]pentachlorophenol in various parts of the fish (total PCP in water 15.6 micrograms/liter) was measured. When the fish were preexposed to KME-Sa + CP, the acute tolerance of this mixture in roach increased by 30-39%, but the response was abolished in 31 days. Fish growth remained unchanged during the experiment. Measurement of PCP accumulation revealed no difference in the absorption rate, but under steady-state conditions the degree of bioconcentration was 16% lower (P less than 0.02) in preexposed roach than in their unexposed controls. This difference was entirely accounted for in the head and visceral parts of the fish. Even when no final changes were noted in tolerance and growth rate of the fish, the authors suggest that the significantly lowered body burden implied acclimatizatory compensation under subchronic exposure of this xenobiotic.

Acclimatization↗
PubMed1990

Uptake and body distribution of chlorinated phenolics in the freshwater mussel, Anodonta anatina L.

Freshwater mussels (Anodonta anatina L.) were exposed to [14C]pentachlorophenol (PCP) and [14C]3,4,5-trichloroguaiacol (CG-3) under laboratory conditions. Uptake and body distribution in mussels as well as total water-soluble metabolites of chlorophenolics in hemolymph and digestive gland were measured. The time course of chlorophenolic accumulation in the mussel soft tissue was followed by analyzing the decrease in the radioactivity in exposure water. The bioconcentration factors (BCFs, activity in animal per activity in water) were measured at steady state for the soft tissue homogenate and separate organs. Both chlorinated phenolics reached a steady-state concentration during the first 24 hr. BCFs in soft tissue ranged from 145 to 342 for PCP and 34 to 125 for CG-3. Accumulations by the digestive gland (hepatopancreas) and kidneys were 2 and 1.3 times greater, respectively, than the average accumulation by the whole soft tissue. The water-soluble fraction of PCP (1-8%) and CG-3 (0.4-2.9%) in separate organs implied only a minor metabolism of chlorophenolics in this animal.

Animals↗
PubMed1991

Interaction of xenobiotics on the glucose-transport system and the Na+/K(+)-ATPase of human skin fibroblasts.

The effects of individual and combined xenobiotics on functional properties of the plasma membrane of human skin fibroblasts were investigated. Good correlations between toxic effects on the D-glucose transport system or the Na+/K(+)-ATPase and the lipophilicity of the substances could be observed. The linear regression coefficients plotting log EC20 values (doses, leading to 20% inhibition) versus log Pow (octanol/water partition coefficient) were r = 0.95 (P less than 0.05). The combination of lipophilic with less lipophilic xenobiotics, such as pentachlorophenol with 4-chloroaniline, leads to additional effects. However, when the detergent sodium dodecyl benzenesulfonate was combined with the herbicide 2,4-dichlorophenoxyacetate (2,4-D), the toxic effect of 2,4-D on the Na+/K(+)-ATPase decreased considerably. The results support in general the assumption that the inhibition of integral functional proteins is based on an accumulation of xenobiotics in the plasma membrane, probably due to the enhanced membrane fluidity. Thus, the basic toxicity of xenobiotics can be predicted by their physicochemical properties.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1995

Mutagenicity of nitroscanate, an antischistosomal drug.

Nitroscanate (NSC) was found to be a direct acting mutagen in the Ames Salmonella tester strains TA100 and TA98 and this activity increased further in the presence of rat liver S9 mix. It was inactive in TA98NR and TA100NR, and weakly active in TA98/1,8-DNP6. A substantial fall in drug induced mutagenicity by pentachlorophenol, an inhibitor of acetyltransferase, in TA98, TA100 and YG1024 suggests the initial bioconversion of a nitro group to hydroxylamine and its further activation to the ultimate N-acetoxyarylamine. The refrigerated DMSO solution of the drug in the plate incorporation assay and freshly prepared solutions using the pre-incubation procedure indicated a fall in mutagenicity owing to the conversion of NSC to N,N'-bis-4-(p-nitrophenoxy)phenyl thiourea (NFPT). The drastic reduction in mutagenicity in the presence of 4-amino-4'-nitrodiphenyl ether (ANDE) and 4-aminodiphenyl ether (ADE) was also attributed to the conversion of NSC to the corresponding thiourea, a non-mutagen. The negligible mutagenicity of ANDE and its absence in ADE and 4-isothiocyanate diphenyl ether (ITDE) suggests that the mutagenicity of NSC is due to the nitro group, and the -NCS function is responsible for enhanced mutagenicity over nor-isothiocyanate 4-nitrodiphenyl ether (NDE).

Acetyltransferases↗
PubMed1983

Effects of chlorinated phenols on immunity in rats.

Female Sprague - Dawley rats were exposed to 0, 5, 50 or 500 ppm 2-chlorophenol (2-CP) or pentachlorophenol (PCP) from weaning to 3 weeks postparturition after breeding at 90 days of age. Progeny were weaned at 3 weeks of age and continued on chlorophenol treatment for 10 weeks at which time major immune functions were tested. Humoral immunity was measured by an indirect ELISA, cell-mediated immunity was monitored by delayed-type hypersensitivity (DTH) to oxazolone, and macrophage function was tested by phagocytosis of sheep red blood cells. Rats treated with cyclophosphamide were included as a positive immunosuppressed control. PCP-treated rats had significantly decreased antibody titers and DTH response and increased induced peritoneal macrophage numbers which displayed hyperphagocytic activity. Immune responses in rats treated with 2-CP were not significantly different from controls. The data indicate that (1) the immune system may be a sensitive target for PCP toxicity but not for 2-CP, (2) closely related chlorophenolic chemical isomers may exert different toxic effects on the immune system, and (3) PCP can exert depressive effects on some major immune parameters while enhancing others.

Animals↗
PubMed1986

Bioconcentration potential of organic environmental chemicals in humans.

A list of environmental chemicals detectable in adipose tissue and/or milk of non-occupationally exposed humans is presented. Besides their physiochemical properties (n-octanol/water partition coefficient and water solubility), their acceptable daily intake (ADI) values, production figures, fate in the environment, concentrations in human adipose tissue, and data from total diet studies from market basket investigations are given. Average bioconcentration factors (BCF) of polychlorinated biphenyls (PCBs), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), DDT, hexachlorobenzene (HCB), dieldrin, hexachlorocyclohexane isomers (alpha-HCH, beta-HCH, gamma-HCH, delta-HCH), pentachlorophenol (PCP), and 3,5-di-tert-butyl-4-hydroxytoluene (BHT) in human adipose tissue are calculated. The bioconcentration factors (wet wt basis) of these compounds are between 3 and 47 times higher in humans than in rats. The environmental chemicals are divided into three groups in respect to their bioconcentration factors in human adipose tissue: group I, high BCF (greater than 100); group II, medium BCF (10-100); and group III, low BCF (less than 10). The bioconcentration factors are useful for hazard assessment of chemicals to humans.

Adipose Tissue↗
PubMed1994

Disposition and metabolism of radiolabelled pentachloroanisole in rats and rabbits.

Male Sprague-Dawley rats and New Zealand White rabbits were administered 14C-labelled pentachloroanisole (PCA) in corn oil by gavage as single doses of 25 mg/kg and were then placed in individual metabolism cages for as long as 4 days. Peak blood level of radioactivity occurred 6 hr after administration of the dose to rats and between 3 and 4 hr in rabbits; the blood elimination half-life ranged from 8 to 15 hr in rats and averaged 6 hr in rabbits. Rats excreted an average of 54.2% of the administered radiolabel in the urine and 32.4% in the faeces during the 96 hr following the dose; rabbits excreted an average of 84.2 and 13.1% of the radiolabel in the urine and faeces, respectively, during this time. Examination of the metabolites in the rat showed that 60% of the urinary radioactivity was attributable to tetrachlorohydroquinone (TCH), 3% to free pentachlorophenol (PCP) and 29% to conjugated PCP; faecal metabolites were PCP (85.7%), TCH (4.3%) and polar metabolite(s) (10%). In the rabbit, 58% of the urinary radioactivity was attributable to TCH, 8% to free PCP and 34% to conjugated PCP. Faecal metabolites consisted of PCP and conjugated material.

Administration, Oral↗
PubMed1994

Genotoxicity of the alkenylbenzenes alpha- and beta-asarone, myristicin and elimicin as determined by the UDS assay in cultured rat hepatocytes.

While the alkenylbenzenes alpha- and beta-asarone are hepatocarcinogenic in rodents, myristicin and elimicin, two other alkenylbenzenes, are not. The present study investigated the mechanism of genotoxicity of the asarones to elucidate the role of cytochrome P-450 and obtain further information about the relationships between the structure, metabolism and genotoxicity of the alkenylbenzenes. The data on the ability of these compounds to induce unscheduled DNA synthesis (UDS) in hepatocytes derived from male Fischer 344 rats are presented in this paper. Cytotoxicity was assessed by lactate dehydrogenase leakage. Elimicin and alpha- and beta-asarone are genotoxic in the UDS assay but myristicin is not. The genotoxicity of the asarones is inhibited by the cytochrome P-450 inhibitor cimetidine but the sulfotransferase inhibitor pentachlorophenol (PCP) is without effect. The major metabolite of the asarones in hepatocytes was identified by liquid chromatography-mass spectrometry as 2,4,5-trimethoxycinnamic acid but this was not genotoxic when tested separately. Simple allylbenzenes such as safrole, estragole and methyleugenol are activated by sequential 1-hydroxylation and sulfation, and this is the likely mechanism of the genotoxicity of elimicin. The propenyl analogues isosafrole, anethole and methylisoeugenol, which cannot undergo 1-hydroxylation, are not genotoxic. The positive results obtained with the asarones suggest the occurrence of a novel activation 'option' for alkenylbenzenes which features a 2-methoxy group in the aromatic ring.

Alkylation↗
PubMed1995

Effects of drinking pattern on the peak/trough blood concentrations in drinking water studies.

The effects of changes in drinking patterns on the expected peak/trough blood concentrations of test compounds were examined during rodent dosed drinking water studies. They were based on the assumption that the kinetics of the test compound is linear and time-invariant. Results indicate that drinking patterns have minor effects on the expected peak/trough concentrations and the time to reach these concentrations. If a 12-hr light/dark cycle starting at 7.00 is used for all the drinking patterns studied, the peak and trough concentrations will occur in the early morning and late afternoon, respectively. A comparison of the predicted versus experimentally determined pentachlorophenol (PCP) plasma concentrations in a 1-wk rat drinking water study revealed that using a circadian rhythm drinking pattern in the model generated the most satisfactory prediction. Predictions based on a square wave drinking pattern with 90% drinking activities in the night phase were also excellent. Triangular or sinusoidal drinking patterns were least accurate in predictions.

Animals↗
PubMed1992

Inhibition of sulfotransferase in primary cultures of human hepatocytes affecting metabolism and binding of 2-acetylaminofluorene.

The metabolism and DNA binding of acetylaminofluorene (AAF) was investigated in human hepatocytes that were isolated from donor liver tissue by collagenase perfusion. Hepatocytes were treated with 0.01 microM pentachlorophenol (PCP), as a sulfotransferase inhibitor, to investigate the role of sulfotransferase in human bioactivation of aromatic amines. Concentrations of PCP greater than 0.1 microM resulted in cytotoxicity as noted by detachment of cells and atypical morphology. The metabolites of AAF were identified by HPLC as aminofluorene, 7-OH-AAF, 9-OH-AAF, 5-OH-AAF, N-OH-AAF, 1-OH-AAF and 3-OH-AAF. No consistent alteration in the metabolites produced occurred with PCP treatment compared to controls. PCP treatment increased total DNA binding of AAF metabolites compared with controls, suggesting that sulfotransferase does not activate AAF in human hepatocytes. Inhibition of sulfotransferase in human hepatocytes does not decrease DNA binding of AAF metabolites as noted previously with rat hepatocytes. Therefore, PCP may inhibit a detoxication pathway. This study supports N,O-acyltransferase as the critical enzyme for the formation of the major reactive metabolite in human liver.

2-Acetylaminofluorene↗
PubMed1984

Transmembrane potential of liver mitochondria from hexachlorobenzene-and iron-treated rats.

The respiratory parameters and the membrane potential of liver mitochondria from rats treated with either hexachlorobenzene, iron or hexachlorobenzene plus iron, to induce experimental porphyria, have been studied. Partial uncoupling of oxidative phosphorylation has been observed in mitochondria from hexachlorobenzene- and hexachlorobenzene plus iron-treated rats. Direct evidence has been presented that this uncoupling is due to the action of pentachlorophenol endogenously formed by metabolism of hexachlorobenzene. No irreversible damage of mitochondria membrane has been revealed under both these conditions. Normal oxidative phosphorylation has been found in mitochondria from rats treated with iron alone. In contrast, they presented an anomalous membrane potential, fully restored by oligomycin. A possible involvement of lipid peroxidation process, induced by iron, in causing these abnormalities has been suggested.

Animals↗
PubMed1981

Effect of phenolic compounds on in vivo activity of glucose-6-phosphatase in certain tissues of Notopterus notopterus.

The effects of phenol (P), dinitrophenol (DNP), pentachlorophenol (PCP), and their three combinations--(PCP + DNP)/P (highly antagonistic), (DNP + P)/PCP (additive) and (P + DNP)/PCP (highly synergistic)-- on glucose-6-phosphatase activity in liver, brain, kidney and gills of Notopterus notopterus were studied at three sub-acute concentrations (1/10, 1/15 and 1/20 the fraction of the 96-h LC50) after 15 and 30 days of exposure. When these chemicals were used separately, PCP exerted more effect than DNP and P. Maximum (71.56%) and highly significant (P less than 0.001) inhibition was observed in liver at the highest concentration of (P + DNP)/PCP combination after 30 days exposure, and lowest (3.64%) and insignificant inhibition in kidney at 1/20 of the (PCP + DNP)/P combination after 15 days exposure. Significant (P less than 0.05, P less than 0.01) stimulation in kidney or no effect in other tissues was observed in lower concentrations of P, DNP and (PCP + DNP)/P.

2,4-Dinitrophenol↗