DIFFERENTIAL-EFFECTS OF NONHYDROXYLATED FLAVONOIDS AS INDUCERS OF CYTOCHROME-P450 1A AND 2B ISOZYMES IN RAT-LIVER

Flavanone, flavone, and tangeretin differentially affected the activit ies of cytochrome P540 1A and 2B isozymes in rat liver. Flavone and, t o a lesser extent, tangeretin, increased activities of ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase, and pentoxyresorufin O- dealkylase (PROD), whereas flavanone mainly enhanced PROD activity. Im munoblot analysis indicated that flavone and tangeretin increased cyto chrome P450 1A1, 1A2, and 2B1,2 forms, whereas flavanone only enhanced the cytochrome P450 2B isozymes. Northern blot study showed that flav one and tangeretin increased the level of the cytochrome P450 1A2 mRNA s. The concentration of the other mRNAs were slightly or not affected by flavonoids. These results suggest that the induction of P450 1A2 by flavone and tangeretin might involve a transcriptional and/or post-tr anscriptional mechanism. (C) 1996 Academic Press, Inc.