Abstract

Cytochrome P450 (CYP) 2E1 is present at very low levels or cannot be detected in rat fetal liver. Experiments were carried out to develop an ex vivo model of CYP2E1 expression in fetal liver. Fetal hepatocytes were prepared from pregnant rats on gestation days ranging from 12 to 19 and placed into culture for 2 days. Expression of CYP2E1 was observed at all gestational periods as evident from immunoblots and oxidation of paranitrophenol and N,N-dimethylnitrosamine by fetal liver microsomes. Northern blot analysis indicated production of CYP2E1 mRNA by the fetal hepatocytes cultured for 2 days but not by freshly isolated fetal rat hepatocytes. The addition of ethanol to the hepatocyte cultures did not have a significant effect on CYP2E1 catalytic oxidation of substrates or CYP2E1 mRNA levels. The content of CYP2E1, CYP2E1 mRNA levels, and CYP2E1 catalytic activity was greater in the fetal cultures grown in the presence of 2.5% fetal calf serum than in that grown with 15% fetal calf serum, suggesting that factors present in the serum limit expression or stability of CYP2E1. CYP2E1 was not detectable in two human fetal livers; however, expression did occur when human fetal hepatocytes were placed into culture for 4 days. These results suggest that cultures of rat and human fetal hepatocytes may be a valuable model with which to study factors that regulate expression of CYP2E1 and the influence of ethanol and other inducers on expression and stabilization of CYP2E1.