Identification of a constitutive form of cytochrome P-450 with high activity towards macrolide antibiotics in Syrian golden hamster liver.

The presence of cytochromes P450 belonging to the P450IIIA family was investigated in the liver of untreated Syrian golden hamsters and compared to those of untreated, phenobarbital- and dexamethasone-treated rats. The microsomal preparations from untreated Syrian golden hamster livers exhibited higher activities of N-demethylation towards the macrolide antibiotics, erythromycin and troleandomycin, than those from untreated and phenobarbital-treated rats. Western blots analysis revealed larger amounts of proteins immunorelated to the rat cytochrome P450IIIA1 isozyme in Syrian golden hamster liver than in untreated and phenobarbital-treated rats. The N-demethylation of erythromycin and troleandomycin were strongly inhibited after preincubation of the microsomes from Syrian golden hamsters with anti-P450IIIA1. We conclude that a cytochrome P450 belonging to the P450IIIA family is expressed constitutively in the liver from Syrian golden hamsters, whereas it is not in rat liver.