Morphological and biochemical analyses of trichloroethylene hepatotoxicity: differences in ethanol- and phenobarbital-pretreated rats.

The histological and biochemical differences between ethanol- and phenobarbital (PB)-potentiated hepatotoxicity of trichloroethylene (TRI) in Wistar strain male rats were investigated. Both ethanol (2 g in daily liquid diet for 3 weeks) and PB (80 mg/kg/day for 4 days, ip) pretreatments enhanced TRI (inhalation exposures of 500 ppm for 8 hr, 2000 ppm for 2 or 8 hr, and 8000 ppm for 2 hr)-induced hepatic damage as judged by increases in plasma transaminase activities. Livers from PB-treated rats exposed to TRI displayed centrilobular necrosis, whereas livers from ethanol-treated rats exposed to TRI were characterized by ballooning degeneration mainly in midzonal areas. TRI exposure decreased the in vitro metabolism of TRI, high-Km benzene aromatic hydroxylase (BAH) activity, and cytochrome P450 content in livers of PB-treated rats with severe hepatic damage. In ethanol-treated rats, TRI exposure increased both the in vitro metabolism of TRI and the low-Km BAH activity but did not cause an apparent decrease in cytochrome P450 content even in animals with severe hepatic damage. These results suggest that TRI caused necrosis of centrilobular hepatocytes in PB-pretreated rats, which was accompanied by loss of xenobiotic metabolizing functions, whereas ballooning degeneration of hepatocytes mainly in midzonal areas occurred in ethanol-pretreated rats without loss of xenobiotic metabolizing functions.