Abstract

To characterize the molecular basis by which imidazole antimycotic drugs increase cytochrome P-450, we examined the effects of treating female rats with clotrimazole, miconazole, or ketoconazole on expression of the major inducible forms of hepatic cytochromes P-450 (P-450p, P-450b/e, P-450c/d, and P-450j). From measurements of the content of immunoreactive cytochromes P-450 in liver microsomes and of the amounts of liver RNA hybridizing to cloned P-450 cDNAs, we established that the glucocorticoid-responsive P-450p is the form predominantly induced by clotrimazole, miconazole, and ketoconazole, to as much as 382 times above control values. The phenobarbital-responsive cytochromes P-450b/e were also induced strongly by clotrimazole and miconazole, but not by ketoconazole. Aromatic hydrocarbon-inducible cytochromes P-450c/d were modestly elevated by each of these three antifungal drugs whereas ethanol-responsive P-450j was marginally induced by ketoconazole, but not by clotrimazole or miconazole. In some, but not all cases, treatment of rats with antifungal drugs resulted in accumulation of P-450 protein that significantly exceeded the increase in the corresponding P-450 mRNA. In conclusion, imidazole antifungal drugs differentially modulate the expression of at least four distinct gene subfamilies of rat hepatic cytochrome P-450 by separate mechanisms involving accumulation of P-450 mRNA and protein.