Although carbon tetrachloride (CCl 4 )-induced acute and chronic hepatotoxicity have been extensively studied, little is known about the very early in vivo effects of this organic solvent on oxidative stress and mitochondrial function. In this study, mice were treated with CCl 4 (1.5 ml/kg ie 2.38 g/kg) and parameters related to liver damage, lipid peroxidation, stress/defense and mitochondria were studied 3 h later. Some CCl 4 -intoxicated mice were also pretreated with the cytochrome P450 2E1 inhibitor diethyldithiocarbamate or the antioxidants Trolox C and dehydroepiandrosterone. CCl 4 induced a moderate elevation of aminotransferases, swelling of centrilobular hepatocytes, lipid peroxidation, reduction of cytochrome P4502E1 mRNA levels and a massive increase in mRNA expression of heme oxygenase-1 and heat shock protein 70. Moreover, CCl 4 intoxication induced a severe decrease of mitochondrial respiratory chain complex IV activity, mitochondrial DNA depletion and damage as well as ultrastructural alterations. Whereas DDTC totally or partially prevented all these hepatic toxic events, both antioxidants protected only against liver lipid peroxidation and mitochondrial damage. Taken together, our results suggest that lipid peroxidation is primarily implicated in CCl 4 -induced early mitochondrial injury. However, lipid peroxidation-independent mechanisms seem to be involved in CCl 4 -induced early hepatocyte swelling and changes in expression of stress/defense-related genes. Antioxidant therapy may not be an efficient strategy to block early liver damage after CCl 4 intoxication.

The cytochrome P-450 content promptly fell in adult rat hepatocytes cultured in conventional conditions whereas no obvious change was detected over a 10-day period when these cells were co-cultured with another rat liver epithelial cell type. A concomitant maintenance of the amino-pyrine N-demethylase activity and a high aflatoxin B1-induced cytotoxicity was observed, and addition of phenobarbital to the culture medium produced about a 2-fold increase in cytochrome P-450 level. These results indicate that when placed in co-culture, adult hepatocytes remain differentiated for several days and suggest that such a co-culture system is an appropriate model for pharmacotoxicological studies.

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