Potenza C L, Pendurthi U R, Strom D K, Tukey R H, Griffin K J, Schwab G E, Johnson E F
Department of Medicine, University of California, San Diego, La Jolla 92093.
J Biol Chem. 1989 Sep 25;264(27):16222-8.
The macrolide antibiotic rifampicin is a potent inducer of cytochrome P-450-mediated drug metabolism in humans and rabbits. In this report, we demonstrate that in immature rabbits, rifampicin activates the transcription of the Cyp3A6 gene which encodes P450IIIA6 (cytochrome P-450 3c). The maximum increase in transcription was seen at 12 h following administration of rifampicin. Northern and slot blot analyses indicate that mRNAs corresponding to P450IIIA6 accumulates during the period of increased transcription and persist at 18 h when the rate of transcription has returned to basal levels. P450IIIA6 protein accumulates in liver microsomes over this period. At 24 h a greater than 10-fold increase in microsomal P450IIIA6 protein is detected by immunoblotting using a monoclonal antibody to P450IIIA6. The rate of microsomal progesterone 6 beta-hydroxylase activity is also elevated when compared to untreated rabbits, and this enzyme is activated in vitro by alpha-naphthoflavone. To determine whether this enzyme is stimulated by alpha-naphthoflavone in intact cells, COS-1 cells were transfected with an expression vector harboring the coding region of a P450IIIA6 cDNA. Our results demonstrate that the transfected COS-1 cells exhibit progesterone 6 beta-hydroxylase activity that is stimulated by alpha-naphthoflavone added to the culture medium.
大环内酯类抗生素利福平是人类和兔子中细胞色素P-450介导的药物代谢的强效诱导剂。在本报告中，我们证明在未成熟兔子中，利福平激活编码P450IIIA6（细胞色素P-450 3c）的Cyp3A6基因的转录。在给予利福平后12小时观察到转录的最大增加。Northern和狭缝印迹分析表明，与P450IIIA6相对应的mRNA在转录增加期间积累，并在转录速率恢复到基础水平的18小时时持续存在。在此期间，P450IIIA6蛋白在肝微粒体中积累。在24小时时，使用针对P450IIIA6的单克隆抗体通过免疫印迹检测到微粒体P450IIIA6蛋白增加超过10倍。与未处理的兔子相比，微粒体孕酮6β-羟化酶活性的速率也升高，并且该酶在体外被α-萘黄酮激活。为了确定该酶在完整细胞中是否受到α-萘黄酮的刺激，用携带P450IIIA6 cDNA编码区的表达载体转染COS-1细胞。我们的结果表明，转染的COS-1细胞表现出孕酮6β-羟化酶活性，该活性受到添加到培养基中的α-萘黄酮的刺激。
