Effects of trichloroethylene on hepatic microsomal enzymes in rats

Cytochrome P-450 levels, cytochrome b_5 levels and NADPH-cytochrome c reductase (P-450 reductase) activities in hepatic microsome of rats were determined after single and repeated administration of trichloroethylene (TRI). Furthermore, the effects of TRI metabolites, chloral hydrate (CH), trichloroethanol (TCE) and trichloroacetic acid (TCA) on the levels or activites of those enzymes investigated. 1.Cytochrome P-450 levels decreased over 10% one or two hours after the single administration of each of 200, 500 and 1,000mg/kg of TRI. A tendency to increase in the enzyme level, however, was observed three hours after the administration. No significant change were seen in cytochrome b_5 level and P-450 reductase activity. 2. The decrease in cytochrome P-450 level was seen also after the single administration of 100mg/kg of CH. It was presumed that the effect of CH on cytocrome P-450 may be concerned in the observed decrease in the enzyme by TRI. 3. No significant changes in the levels or activity of the three enzymes were seen after the single administration of each of TCE and TCA. 4. The mixed function oxidase system was induced after the repeated administration of TRI. It is presumed that hepatotoxicity of TRI may be enhanced by chronic exposure to the solvent.