Blink reflex latency after exposure to trichloroethylene in well water

The electrophysiological measurement of the blink reflex (BR) can quantify the conduction latency in the reflex arc involving the Vth (trigeminal) and VIIth (facial) cranial nerves. We measured the electrophysiological BR in a population (N = 21), which had alleged chronic exposure to trichloroethylene (TCE) through the public drinking water at levels 30-80 times higher than the Environmental Protection Agency (EPA) Maximum Contamination Level (MCL). A highly significant difference was observed in the conduction latency means of the BR components (p less than .0001), when the study population was compared with laboratory controls (N = 27). This difference suggests a subclinical alteration of the Vth cranial nerve function due to chronic, environmental exposure to TCE.

Regeneration of the sciatic nerve in mice and rats exposed to trichloroethylene

The effects of trichloroethylene (TCE) on regeneration of the sciatic nerve after a crush lesion was tested in mice and rats. A lesion was made on nerves in unexposed animals and in animals pre-exposed to TCE for 20 days. Experimental animals were then exposed to TCE for an additional 4 days. Exposures were continuous at 150 or 300 ppm. Regeneration was measured by pinching the outgrowing nerve fibers. Regeneration was retarded in the TCE-exposed animals compared to the air-exposed controls. Mice were more sensitive to TCE exposure than rats. Liver weight increased in TCE-exposed mice but there was no correlation between this effect and that on nerve regeneration.

Trichloroethylene and halothane inhibit uptake and metabolism of 5-hydroxytryptamine in rat lung slices

The effect of exposure to organic solvents on uptake and metabolism of 5-HT was studied in rat lung slices. It was found that under control conditions 5-HT was both taken up and metabolized to 5-HIAA. When halothane (35,000 ppm) or trichloroethylene (18,000 ppm) were equilibrated with the incubation medium the uptake of 5-HT decreased by approximately 50% after 30 min of incubation, and the production of 5-HIAA was inhibited by approximately 70% and 80%, respectively. The results are consistent with earlier studies using a much more elaborate technique, in which halothane and trichloroethylene were found to depress 5-HT uptake in isolated perfused rat lungs. Our results demonstrate that the simpler technique employing lung slices can also be used, to investigate factors affecting pulmonary uptake of endogenous amines, and, potentially, the uptake of other compounds as well.

Trichloroethylene inhibits uptake of 3H-5-hydroxytryptamine but not uptake of 3H-zimeldine or 3H-propranolol in isolated perfused rat lungs

Pulmonary uptake of 5-hydroxytryptamine (5-HT), zimeldine and propranolol were studied using the isolated perfused rat lung model. The 5-HT uptake was found to be attenuated by approximately 50 per cent in comparison to the control, when the lungs were ventilated with air containing 5,000 p.p.m. trichloroethylene. In experiments in which the active uptake of 5-HT was blocked with the selective 5-HT uptake inhibitor zimeldine (5 X 10(-6) M), the uptake of 5-HT decreased by 70 +/- 1.7 per cent (mean +/- S.E.M.). When trichloroethylene (5,000 p.p.m. and 18,000 p.p.m.) was added, no further decrease in uptake was noted. The uptake of 3H-zimeldine (10(-6) M) and 3H-propranolol (10(-6) M) was unaffected by ventilating the lungs with trichloroethylene. It is concluded that trichloroethylene inhibits the active uptake of 5-HT from the pulmonary circulation, but that it has no effect on the uptake of zimeldine or propranolol, which are taken up predominantly by passive diffusion.

Effects of trichloroethylene, tetrachloroethylene and dichloromethane on soil biomass and microbial counts

Trichloroethylene, tetrachloroethylene and dichloromethane in concentrations of 10, 100, and 1000 micrograms per 100 g brown soil (dry weight) had different effects on soil microorganisms. The ATP content of the soil biomass decreased significantly in the first and second week of incubation when 100 micrograms of trichloroethylene and tetrachloroethylene were added to the soil, and it was strongly reduced during the two months of the experiment duration when 1000 micrograms of the individual chlorinated solvents under test was added. Similar inhibitory effects could be observed with soil fungi. Tetrachloroethylene in a dose of 1000 micrograms, however, exerted mainly a stimulative influence as shown by the counts of oligotrophic and copiotrophic aerobic soil bacteria and also by the total counts of anaerobic microorganisms. The same concentrations of trichloroethylene and dichloromethane inhibited both groups of aerobic bacteria in the soil. Actinomycetes were mainly inhibited by addition of 1000 micrograms of the volatile chlorinated solvents but they were not affected by lower concentrations. No significant effects were observed in aerobic spore-forming bacteria, and only slight effects were found also in the spore-forming anaerobic microorganisms of Clostridium sp. In conclusion, with the concentrations of chlorinated solvents which were from 10(3) to 10(6) higher than the actual 'in situ' soil contamination, some negative effects on soil microorganisms could be observed. However, one or two month after the soil was contaminated, the microbial counts increased again.

Bacterial beta-lyase mediated cleavage and mutagenicity of cysteine conjugates derived from the nephrocarcinogenic alkenes trichloroethylene, tetrachloroethylene and hexachlorobutadiene

The metabolism of beta-lyase and the mutagenicity of the synthetic cysteine conjugates S-1,2-dichlorovinylcysteine (DCVC), S-1,2,2-trichlorovinylcysteine (TCVC), S-1,2,3,4,4-pentachlorobuta-1,3-dienylcysteine (PCBC) and S-3-chloropropenylcysteine (CPC) were investigated in Salmonella typhimurium strains TA100, TA2638 and TA98. The bacteria contained significantly higher concentrations of beta-lyase than mammalian subcellular fractions. Bacterial 100,000 X g supernatants cleaved benzthiazolylcysteine to equimolar amounts of mercaptobenzthiazole and pyruvate. DCVC, TCVC and PCBC produced a linear time-dependent increase in pyruvate formation when incubated with bacterial 100,000 X g supernatants; pyruvate formation was inhibited by the beta-lyase inhibitor aminooxyacetic acid (AOAA). CPC was not cleaved by bacterial enzymes to pyruvate. DCVC, TCVC and PCBC were mutagenic in three strains of S. typhimurium (TA100, TA2638 and TA98) in the Ames-test without addition of mammalian subcellular fractions; their mutagenicity was decreased by the addition of AOAA to the preincubation mixture. CPC was not mutagenic in any of the strains of bacteria tested. These results indicate that beta-lyase plays a key role in the metabolism and mutagenicity of haloalkenylcysteines when tested in S. typhimurium systems. The demonstrated formation in mammals of the mutagens DCVC, TCVC and PCBC during biotransformation of trichloroethylene (Tri), tetrachloroethylene (Tetra) and hexachlorobutadiene (HCBD) may provide a molecular explanation for the nephrocarcinogenicity of these compounds.

Covalent binding to apoprotein is a major fate of heme in a variety of reactions in which cytochrome P-450 is destroyed

The heme in rat liver microsomal cytochrome P-450 was labeled with 14C or 3H and the microsomes were fractionated after in vitro incubations with a variety of agents known to destroy cytochrome P-450 heme. A major fraction of the heme label was irreversibly bound to apoprotein in all cases, including incubations with fluroxene, 1-octene, vinyl bromide, trichloroethylene, vinyl chloride, parathion, cumene hydroperoxide, NaN3, or iron-ADP complex. Label was also extensively bound to apoprotein when purified and reconstituted cytochrome P-450 was incubated with NADPH and vinyl chloride. This process appears to be widespread and involved to a significant extent in the cytochrome P-450 heme destruction observed with many compounds.

[Negative report on trichloroethylene-induced pneumatosis cystoides intestinalis in rats]

In recent years it has been suggested in Japan that occupational trichloroethylene exposure will induce primary pneumatosis cystoides intestinalis coli. A series of two experiments were conducted to ascertain the cause-effect relationship between trichloroethylene and pneumatosis as follows: In the first experiment, 12 male rats of Fischer strain were exposed to trichloroethylene at a nearly lethal concentration for 12 wk. Five out of 12 rats died during the experiment, and body weight gain was extremely depressed. However, neither pneumatosis nor histological changes were observed. No changes were observed in 4 control rats as well. In the second experiment, 38 male rats of Sprague-Dawley strain were exposed to 800, 200 or 50 ppm trichloroethylene over a period of 12 wk. Two out of 13 rats of the 800 ppm group died, and body weight gain was suppressed. Mild suppression in body weight gain was also observed in the 200 ppm group. However, pneumatosis was not observed in any rats of trichloroethylene groups. No pathological changes were observed in 13 rats of the control group. The foregoing results suggest that trichloroethylene cannot induce pneumatosis cystoides intestinalis in rats of these two strains. Inasmuch as rats are not prone to develop pneumatosis, the possibility for trichloroethylene to induce this disease in man cannot be denied.

[Biochemical mechanisms of the effect of low molecular weight organochlorine aliphatic compounds on humans and animals (review)]

Data on the effects of 1,1,1-trichlorethane and tetrachlorethylene on human and animal organisms are reviewed. These compounds are used in industry and in homeservice. The review deals with some aspects of the action of these organic solvents at the subcellular level.

Effects of trichloroethylene on the human vestibulo-oculomotor system

Ten healthy volunteers were subjected to a vestibulo-oculomotor test battery before, during and 1 hour after trichloroethylene exposure. The concentration of trichloroethylene in inspiratory air was 32-78 ppm (176-429 mg/m3). The concentration of trichloroethylene in venous blood was followed throughout the experiment. The mean pulmonary uptake was estimated. Each test person was also subjected to a control experiment, breathing air free of trichloroethylene. A decreased ability to visually suppress the vestibulo-oculomotor reflex during sinusoidal stimulation was noticed during trichloroethylene exposure. One hour after exposure the test subjects showed a decreased maximum velocity of the voluntary saccade and a decreased ability to follow a sinusoidally moving target.

Trichloroacetic acid accumulates in murine amniotic fluid after tri- and tetrachloroethylene inhalation

The distribution of trichloroethylene (Tri) and tetrachloroethylene (Tetra) and their metabolites have been studied in pregnant mice by means of whole-body autoradiography (14C-labelled Tri and Tetra) and gas chromatography, with special emphasis on possible uptake and retention in the foetoplacental unit. Volatile (non-metabolized) activity appeared at short intervals after a 10 min. or 1 hr inhalation period in foetus and amniotic fluid. Most notable, however, was a strong accumulation and retention (peak at 4 hrs) in amniotic fluid of the metabolite trichloroacetic acid (TCA) after inhalation of either of the solvents. The main metabolite of Tri, trichloroethanol (TCE) (or conjugates), did not accumulate specifically as compared to maternal plasma. TCA infused intravenously in the maternal plasma was accumulated in amniotic fluid, but less pronounced than after Tri and Tetra inhalation, indicating that some metabolism of Tri and Tetra to TCA may occur in the foetoplacental unit. The results suggest that TCA may be transported to the foetus partly paraplacentally through foetal membranes and amniotic fluid, with the possibility of foetal swallowing or absorption through the skin. Foetal urinary activity also suggests that circulation between foetus and amniotic fluid may contribute to the long-term retention in the foetoplacental unit. In the mother, after inhalation exposures, and in intraperitoneally injected newborn mice, non-extractable radioactivity was found in the respiratory tract, liver, and kidney, indicating binding to these organs through metabolism.

The c-wave of the electroretinogram and the standing potential of the eye as highly sensitive measures of effects of low doses of trichloroethylene, methylchloroform, and halothane

Low and moderate intravenous doses of trichloroethylene, methylchloroform, and halothane dissolved in a lipid emulsion (Intralipid) were given to cynomolgus monkeys. The DC electroretinogram (ERG) and the standing potential of the eye (SP) were recorded directly with corneal contact lenses, very stable calomel electrodes, and under very constant general anesthesia. Even low doses of the substances (close to the hygienic threshold limit values in Sweden) clearly provoked slow variations with time in the amplitude of the c-wave of the ERG and in the SP level. Both potentials are generated mainly in the pigment epithelium. It is suggested that the effects reflect a direct influence of the chemicals upon the metabolism of the pigment epithelium or on the cell membrane. Thus the method used is a highly sensitive measure of effects of certain halogenated hydrocarbons on structures belonging to the central nervous system.

Biochemical, histological, and ultrastructural changes in rat and mouse liver following the administration of trichloroethylene: possible relevance to species differences in hepatocarcinogenicity

Trichloroethylene (TRI), administered by gavage for 10 consecutive days, at doses of 500 to 1500 mg/kg body wt increased liver weight (175% of control), decreased hepatic DNA concentration (66% of control), and increased the synthesis of DNA (500% of control; as measured by [3H]dT incorporation) in B6C3F1 mice and Alderley Park mice. Similar treatment of Osborne-Mendel rats or Alderley Park rats resulted in smaller increases in liver weight (130% of control) and decreases in DNA concentration (83% of control). No effect of TRI on DNA synthesis was seen in rats. The increased DNA synthesis in the mouse was not apparently due to regenerative hyperplasia since no signs of necrosis were seen. Furthermore the increased [3H]dT incorporation probably represented semiconservative replication of DNA and not repair, since a parallel increase of mitotic figures was observed. Hence, the liver growth noted after TRI administration appears to be due to liver cell enlargement (hypertrophy) in the rat, but both hypertrophy and hyperplasia (cell proliferation) in the mouse. An important observation has been that TRI induced the peroxisomal enzyme activities, catalase, and cyanide-insensitive palmitoyl-CoA oxidation (147 and 786% of control, respectively), in mice but not in rats. Furthermore, increases in peroxisome volume density (up to 1110% of control) were observed in mice receiving TRI. These observations lead us to suggest that the species difference in hepatocarcinogenicity of TRI, seen between the rat and mouse, is possibly due to a species difference in peroxisome proliferation and cell proliferation, the peroxisome proliferation leading to increased reactive oxygen species and DNA damage, and the cell proliferation then acting to promote this lesion.

Immunochemical evidence for induction of the alcohol-oxidizing cytochrome P-450 of rabbit liver microsomes by diverse agents: ethanol, imidazole, trichloroethylene, acetone, pyrazole, and isoniazid

Isozyme 3a of rabbit liver microsomal cytochrome P-450, also termed P-450ALC, was previously isolated in this laboratory from animals administered ethanol or imidazole, and the purified cytochrome was shown to function in the reconstituted system as an oxygenase in catalyzing the oxidation of ethanol and other alcohols. Although liver microsomes from animals treated in various ways exhibit increased alcohol-oxidizing activity, evidence was not available as to whether this was due to enzyme induction or to other factors influencing the activity. Immunochemical quantitation of P-450 isozyme 3a has now been achieved by use of purified antibody to this cytochrome in NaDodSO4/PAGE/blotting and dot-blotting techniques. The specific content of isozyme 3a in liver microsomes was found to be increased from 2- to greater than 4-fold by administration of the following agents, in increasing order of effectiveness as inducers: isoniazid, trichloroethylene, pyrazole, ethanol, imidazole, and acetone. Isozyme 3a represents about 5% of the total P-450 in control animals and is increased to as high as 27% by acetone treatment. Isozyme 3a-dependent butanol-oxidation activity, determined by the inhibitory effect of antibody on the various microsomal preparations, was found to increase proportionally with increased content of this cytochrome.

Mutagenicity of trichloroethylene, trichloroethanol and chloral hydrate in Aspergillus nidulans

A trichloroethylene (TCE) sample, free of epoxides, has been assayed for its ability to induce gene mutations (methionine suppressors) and mitotic segregation in the mould Aspergillus nidulans. No increase in the spontaneous frequency of methionine suppressors was observed when conidia of a haploid strain were plated on selective medium and exposed to TCE vapours. A weak but statistically significant increase in methionine suppressors was detected, however, when conidia of cultures grown and conidiated in the presence of TCE vapours were plated onto selective media. Growing colonies of a heterozygous diploid strain were exposed to TCE vapours to investigate the induction of mitotic segregation. Scoring and phenotypic analysis of segregant sectors showed a significant increase in the frequency of haploids and 'non-disjunctional' diploids but not of cross-overs. Treatment of quiescent conidia in liquid medium was ineffective. Trichloroethanol and chloral hydrate, two main TCE metabolites in mammals, shared the ability to induce somatic segregation demonstrated by TCE vapours. On the grounds of these results the possible endogenous metabolic conversion of TCE into trichloroethanol and chloral hydrate is hypothesized.

Serum enzymes in toxicity of trichloroethylene after subchronic ethanol pretreatment

In order to establish evidence of serum enzyme activities in toxicological long-term experiments alterations of alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) in the serum of rats were investigated after subchronic ethanol pretreatment and following trichloroethylene exposure. Somewhat lower enzyme activities were found in ethanol treated animals than in those who only got water in nearly all cases. Significant ALAT and ASAT decreases occurred after giving higher ethanol concentrations (5% and 10%, v/v) for 30 weeks. It is possible that this fact among other things could be responsible for the only slight enzyme elevations after trichloroethylene in long-term ethanol pretreated rats.

Species differences in carcinogenicity and peroxisome proliferation due to trichloroethylene: a biochemical human hazard assessment

Trichloroethylene (TRI) administered to mice by gavage for 10 consecutive days at doses of 50-2000 mg/kg body weight elicited dose-dependent increases (up to 700% of control values) of hepatic cyanide insensitive palmitoyl CoA oxidation (a marker of peroxisomal beta-oxidation). No effect was seen on catalase; the other peroxisomal marker examined. Similar experiments with rats demonstrated no effect of TRI on either cyanide insensitive palmitoyl CoA oxidation or catalase. A major metabolite of TRI, trichloroacetic acid (TCA) when administered by gavage for 10 consecutive days at doses of 10-200 mg/kg body weight, stimulated hepatic cyanide insensitive palmitoyl CoA oxidation in both mice (up to 500% of control) and rats (up to 650% of control). Again, no effect upon catalase activity was apparent. The kinetics of biotransformation of TRI to TCA in isolated hepatocytes was markedly species dependent. The 'intrinsic clearance' values (Vmax/Km) for TRI in mouse, rat and human hepatocytes were 3.8 X 10(-6), 1.2 X 10(-7) and 3.25 X 10(-8) L/min/10(6) cells respectively. TCA induced peroxisomal beta-oxidation in mouse and rat hepatocytes, but had no effect upon this enzyme activity in cultured human hepatocytes. It is postulated that the species difference in hepatocarcinogenicity of TRI (mouse positive; rat negative) is due to species differences in peroxisome proliferation which in turn is a result of differences in the rate of formation of TCA from TRI. On this basis it is proposed that TRI presents no significant human hepatocarcinogenic hazard since, human hepatocytes produced TCA at a rate even lower than that of the rat, and TCA was not a peroxisome proliferator in human hepatocytes.

Trichloroethylene effects on the formation of enzyme-altered foci in rat liver

The initiating and promoting effects of trichloroethylene in rat liver were investigated using the enzyme-altered foci bioassay. The incidence of gamma-glutamyl transpeptidase (GGT)-positive foci was used as an early histochemical marker of putative preneoplastic hepatocytes. A single PO dose of trichloroethylene (490 mg/kg) was administered in corn oil to rats which had been partially hepatectomized 24 h previously. Three days following gavage with the chlorinated hydrocarbon the rats were promoted with an 8-week regimen of 500 ppm phenobarbital in drinking water. This protocol is known to induce enzyme-altered foci in the livers of animals which have received an initiating dose of a genotoxic carcinogen. Trichloroethylene was not found to induce GGT-positive foci under these conditions. Additionally, groups of rats were partially hepatectomized, initiated with N-nitrosodiethylamine (30 mg/kg; PO) and administered five times weekly doses of 200 mg trichloroethylene per rat in order to investigate the promoting activity of the chlorinated hydrocarbon in rat liver. No significant promoter effects were observed with trichloroethylene, although the results in this case were somewhat equivocal. The findings of these investigations are taken as partially supportive of an epigenetic, cytotoxic mechanism of tumorigenic action of trichloroethylene.

Inhibition of delta-aminolevulinic acid dehydratase by trichloroethylene

Male Wistar rats (8 animals/group; 180-200 g) were exposed continuously to trichloroethylene (TRI) for 48 or 240 h or methylchloroform (1,1, 1-trichloroethane: MC for 48 h at 50, 400 and 800 ppm. The inhibition of delta-aminolevulinic acid dehydratase (ALA-D) was examined in liver, blood and bone marrow of naive and phenobarbital pretreated animals exposed to TRI. A clear cut dose-effect relationship between the exposure concentration or duration of exposure and the inhibition of ALA-D activity was seen for rats exposed to TRI. In addition to this finding, significant interaction between TRI exposure and phenobarbital treatment was observed in the inhibition of ALA-D in liver and blood. MC did not produce inhibition. Trichloroacetic acid and trichloroethanol failed to inhibit the ALA-D activity in vitro. It seems that a metabolite(s) of TRI other than the above 2 substances may play a role in the inhibition of ALA-D. The inhibition of ALA-D (38% or 48% of the control in liver or in blood, respectively) observed after the 240 h exposure at 400 ppm to TRI was accompanied by the significant elevation of delta-aminolevulinic acid synthase (186% of the control) in liver and the increase in excretion of delta-aminolevulinic acid in urine (142% of the control). This occurred without an apparent weight loss, liver injury or hematological changes.

[Interaction of solvent effects on the plasma membrane]

The combined effect of trichloroethylene and butanol on the behaviour of human erythrocytes during haemolysis in hypotensive milieu was investigated in comparison to the individual effects of solvents. In these cases, among others, appeared statistically significant quantitative changes of the maximum of stability. In a common influence of trichloroethylene and butanol and additional stabilisation of the membrane may be the result, which is traced back to various places of effect of the solvents. When 150 mmol/l butanol are used the haemolysis is suppressed by trichloroethylene in its concentration region of 8-10 mmol/l. This effect can be explained by additional inclusion of trichloroethylene in butanol-free lipid classes. When 200 mmol/l butanol are given the haemolysis much increases already at an application of 4 mmol/l trichloroethylene. Here trichloroethylene cannot infiltrate into other still butanol-free lipid classes, in order to evoke an additional stabilisation. On the contrary, in cooperation the decomposition of the crystal structure of the lipids (emulsification) and thus the haemolysis develops. These results refer to the fact that combined effects of solvents are not always to be valuated additively.

Some effects of trichloroethylene on mouse lungs and livers

Repeated administration of trichloroethylene (TCE) to mice by either i.p. injection or by inhalation increased the activity of hepatic microsomal NADPH cytochrome-c reductase. The NADPH cytochrome c reductase activity in microsomes isolated from lungs of animals treated with TCE by inhalation was decreased relative to controls (untreated animals). TCE inhalation was associated with pathologic changes in lungs, but not in livers of the treated animals. The duration of exposure is probably an important factor however, since animals exposed for only 1 hr per day exhibited neither pathologic changes in the lungs nor an alteration of enzyme activity. These findings indicate that inhalation of TCE, without prior treatment with inducers, can enhance activity of the hepatic mixed function oxidase system. The reduced activity of the pulmonary mixed function oxidase system in animals that inhaled TCE may reflect injury to the lungs.

Effects of trichloroethylene exposure on hearing. An investigation of cochlear microphonics and action potential of the guinea pig

Four groups of guinea pigs with normal Preyer's reflex were exposed to trichloroethylene (TCE). Each group consisted of nine to 10 naive male albino Hartley guinea pigs of 9 weeks of age with a body weight of approximately 400 g. To test the suggestion that TCE causes damage to the cochlear system, a study was conducted involving four experiments. The results were as follows: No significant difference was observed between the intensity functions of the CM (4 kHz) and AP (7 kHz) potentials of the control groups and those of the TCE-exposed groups by analysis of variance. It was considered that there was no difference in the cochlear reaction to high frequency sound between guinea pig and man. It therefore might be suggested that acute exposure to TCE of a high concentration does not always induce dysfunction of the organ of Corti and the 8th nerve in man.

Day-case anaesthesia for termination of pregnancy. Evaluation of a total intravenous anaesthetic technique

An investigation was undertaken to assess the use of a total intravenous anaesthetic technique of fentanyl and methohexitone for outpatient vaginal termination of pregnancy. When compared with a technique of fentanyl, methohexitone, nitrous oxide and trichloroethylene the total intravenous method caused swifter recovery, minimal side-effects and no cardiovascular depression. However, both anaesthetic techniques produced significant postoperative reduction of memory for new facts when compared with a control group receiving no general anaesthesia. There is a need to continue the search for anaesthetic methods appropriate for day cases.