INDUCTION, SUPPRESSION AND INHIBITION OF MULTIPLE HEPATIC CYTOCHROME-P450 ISOZYMES IN THE MALE-RAT AND BOBWHITE QUAIL (COLINUS-VIRGINIANUS)BY ERGOSTEROL BIOSYNTHESIS INHIBITING FUNGICIDES (EBIFS)

Ergosterol biosynthesis inhibiting fungicides (EBIFs) have complex eff ects on the hepatic microsomal monooxygenase systems of vertebrate spe cies, having been described as mixed inducers and inhibitors of cytoch rome P450. In the current study, we examined the effects of two EBIF's in clinical use, clotrimazole and ketoconazole, and two agricultural EBIFs, propiconazole and vinclozolin, on hepatic monooxygenase activit ies and P450 apoprotein expression in the male Sprague-Dawley rat and the male bobwhite quail. EBIFs produced Type II binding spectra with h epatic microsomes from both species and were effective inhibitors of m ethoxyresorufin O-demethylase, an activity selective for P450 isozymes in gene family 1. However, the EBIFs varied widely in their effective ness as inducers of P450 isozymes in gene families 1, 2, 3 and 4, both within the same species and between species. In the rat, clotriamzole was the most effective inducer, increasing expression of CYP 3A isozy mes over 450-fold, CYP 2B1/2 30-fold and CYP 1A1/2 12-fold and suppres sing expressing of CYP 2C11 nearly 70%. By contrast, in the quail, clo trimazole was the least effective inducer. In quail, vinclozolin and p ropiconazole elevated total P450 content 10- and 7-fold, respectively. The induction response also appeared to be mixed, but in this case co nsisted of a 5-fold induction of P450s in gene family 1A, a 3-fold ind uction of P450s in gene family 3A and 4A, and induction of proteins(s) from gene family 2, cross-reactive with antisera against rate CYP 2C1 1 and CYP 2A1. A protein that was cross-reactive with antibodies raise d against rat CYP 2B1 was decreased with EBIF treatment. In conclusion , EBIFs have complex patterns of induction, suppression and inhibition of cytochrome P450 isozymes in both mammals and birds which vary acco rding to both the fungicide and the species.