Effects of ethanol and clofibrate on expression of cytochrome P‐450 enzymes and epoxide hydrolase in cultures and cocultures of rat hepatocytes

Cultured and cocultured rat hepatocytes were used to study the effects of ethanol and clofibrate on cytochrome P‐450 (P‐450) enzymes and epoxide hydrolase. We showed that in the presence of ethanol, clofibrate or both compounds, rat hepatocytes were able to express, after 3 days of pure culture, quantitatively and qualitatively reasonable levels of most cytochrome P‐450 enzymes and epoxide hydrolase, compared to freshly isolated hepatocytes. However, ethanol induced the P‐450IA subfamily, and clofibrate the P‐450‐IVA subfamily. In cocultures, after 6 days, most P‐450 enzymes were still expressed while P‐450IIC11 was completely lost. Ethanol and clofibrate had the same effect as in pure culture. These results show, by modifying culture medium conditions and cell‐cell interactions, that it is possible to maintain reasonable xenobiotic‐metabolizing‐enzyme expression; however, these conditions have to be improved in order to preserve better P‐450 expression. The mechanism of these effects and the inducibility of these systems remain to be elucidated by a study at molecular level.