Multiple forms of cytochrome P-450 (III): Inductory mode of cytochrome P-450 from rat liver microsomes treated with phénobarbital

Abstract

We demonstrate the induction manner of rat liver microsomal cytochrome P-450 treated with phénobarbital (PB) from the amino-pyrine (AP) demethylase and benzo(a)pyrene (BP) hydroxylase activity and from the high-performance liquid chromatography (HPLC) profiles. The content of cytochrome P-450 started to increase at 8 hr after administration of PB (100mg/Kg) and kept increasing continuously. At 48 hr, specific content of cytochrome P-450 elevated to about twice that of non-treated microsomes. AP demethylase activity increased as contents of cytochrome P-450 increased. However, BP hydroxylase activity did not change. Distinct change was not observed in the content of cytochrome b5- by the induction with PB; however, slight elevation was detected at 48 hr. Two different forms of cytochrome P-450 (PB-4 and PB-5) induced by PB were observed in HPLC profile and collected separately. Absolute spectrum of these forms were almost the same. Molecular weights of PB-4 and PB-5 calculated by SDS-PAGE were distinct, i.e., 51,000 and 53,000, respectively. The peaks of PB-4 and PB-5 were not observed as a definite peak in the HPLC profile of non-treated microsomes. The peaks of PB-4 and PB-5 were detected distinctly as a peak of cytochrome P-450 at 8 hr and 24 hr, respectively.