Wang R W, Kari P H, Lu A Y, Thomas P E, Guengerich F P, Vyas K P
Department of Animal and Exploratory Drug Metabolism, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065.
Arch Biochem Biophys. 1991 Nov 1;290(2):355-61. doi: 10.1016/0003-9861(91)90551-s.
Previous studies from our laboratories have shown that the metabolism of the cholesterol-lowering drug lovastatin by rat and human liver microsomes occurs primarily at the 6'-position, giving 6' beta-hydroxy- and 6'-exomethylene-lovastatin and that these oxidations are catalyzed by cytochrome P450-dependent monooxygenases. In the present study, the specific cytochrome P450 form involved in lovastatin oxidation was identified through immunoinhibition studies. Among several antibodies prepared against various cytochrome P450s, only anti-rat P450 3A IgG inhibited lovastatin metabolism in liver microsomes from untreated, phenobarbital-treated, and pregnenolone-16 alpha-carbonitrile-treated rats. Lovastatin metabolism at the 6'-position was markedly inhibited (6' beta-hydroxy, greater than 95%; 6'-exomethylene, 70-80%) by this antibody whereas the effect of anti-rat P450 3A on the 3"-hydroxylation was variable depending on the source of the microsomes. With human liver microsomes, both anti-rat P450 3A and anti-human P450 3A inhibited lovastatin metabolism. Correlation between lovastatin oxidation and the P450 3A content in human liver microsomes (measured by immunoblot analysis) was excellent (r2 = 0.97). In addition, preincubation of human liver microsomes with troleandomycin and NADPH inhibited metabolism by 60%. These results clearly indicate that cytochrome P450 3A enzymes are primarily responsible for the metabolism of lovastatin in rat and human liver microsomes.
我们实验室之前的研究表明，大鼠和人肝脏微粒体对降胆固醇药物洛伐他汀的代谢主要发生在6'-位，生成6'-β-羟基洛伐他汀和6'-亚甲基洛伐他汀，并且这些氧化反应由细胞色素P450依赖性单加氧酶催化。在本研究中，通过免疫抑制研究确定了参与洛伐他汀氧化的特定细胞色素P450形式。在针对各种细胞色素P450制备的几种抗体中，只有抗大鼠P450 3A IgG抑制未处理、苯巴比妥处理和孕烯醇酮-16α-腈处理大鼠肝脏微粒体中的洛伐他汀代谢。该抗体显著抑制了6'-位的洛伐他汀代谢（6'-β-羟基，大于95%；6'-亚甲基，70 - 80%），而抗大鼠P450 3A对3"-羟基化的影响则因微粒体来源而异。对于人肝脏微粒体，抗大鼠P450 3A和抗人P450 3A均抑制洛伐他汀代谢。人肝脏微粒体中洛伐他汀氧化与P450 3A含量（通过免疫印迹分析测定）之间的相关性极佳（r2 = 0.97）。此外，人肝脏微粒体与三乙酰竹桃霉素和NADPH预孵育可使代谢抑制60%。这些结果清楚地表明，细胞色素P450 3A酶是大鼠和人肝脏微粒体中洛伐他汀代谢的主要原因。
