POSSIBLE EXISTENCE OF A CYP3A PROTEIN IN LIVER-MICROSOMES FROM FEMALERATS

CYP3A proteins are P450 monooxygenases involved in the metabolism of s teroids, retinoic acid and several important drugs. In rats, the numbe r of CYP3A genes and proteins, and therefore important aspects of thei r inducibility, developmental regulation and sex specificity are not k nown for certain. Using triacetyloleandomycin-metabolite complex forma tion, testosterone hydroxylase assays and immunoblots from peptide map s, we obtained results suggesting that in liver microsomes from mature rats, at least three, possibly four CYP3A proteins are expressed: one is present in females, another is male-specific, and one or two addit ional CYP3A proteins are inducible by phenobarbital, steroids, and tri acetyloleandomycin.