Effects of AFB1 on CYP 1A1, 1A2 and 3A6 mRNA, and P450 expression in primary culture of rabbit hepatocytes

Although numerous studies report strong hepatic cytochrome P450 decrease du ring aflatoxicosis, the mechanisms involved in this decrease remain to be e stablished. The purpose of this work is to investigate whether decreased CY P mRNA expression could explain decreased P450 expression and activity. Stu dies were conducted in primary cultures of rabbit hepatocytes exposed to 0. 1 and 1 mu M aflatoxin B1 (AFB1) incubated in the culture medium for 72 h. In order to confirm the effects of the mycotoxin, 30 mu M beta-naphthoflavo ne or rifampicin were used as respective inductors of P450 1A1 and 1A2 or 3 A6. Dose-dependent decreases of CYP mRNA expression were observed in all AF B1-treated cells; however, these decreases were not specific. Moreover, P45 0 expression and activity are far less decreased by the AFB1 treatment than their corresponding mRNA. Taken together, these results suggest that the s pecific P450 decrease observed during aflatoxicosis was not the consequence of a specific decrease of their mRNA expression. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.