Xu D, Voigt J M, Mico B A, Kominami S, Takemori S, Colby H D
Department of Pharmacology and Toxicology, Philadelphia College of Pharmacy and Science, PA 19104.
Biochem Pharmacol. 1994 Oct 7;48(7):1421-6. doi: 10.1016/0006-2952(94)90566-5.
Studies were done to determine the effects of a P450 suicide inhibitor, 1-aminobenzotriazole (ABT), on adrenal steroid and xenobiotic metabolism. Incubation of guinea pig adrenal microsomes with ABT plus an NADPH-generating system caused a time-dependent decline in total P450 concentrations. The maximal decrease in P450 levels was approximately 35% and was accompanied by an equimolar decrease in heme content. Western blot analyses indicated that ABT had no effect on P450 apoprotein levels. Benzphetamine (BZ) N-demethylase and benzo[a]pyrene (BP) hydroxylase activities were inhibited almost completely by microsomal incubations with ABT. In contrast, neither steroid 17 alpha-hydroxylase nor 21-hydroxylase activity was affected by ABT. The steroid-induced type I spectral change in adrenal microsomes also was not affected by ABT, whereas that induced by BZ was eliminated. Similar studies with adrenal mitochondria indicated that ABT had no effect on mitochondrial P450 concentrations or on mitochondrial steroid metabolism. The results demonstrate that the in vitro actions of ABT on adrenal cytochromes P450 are highly selective for those isozymes that catalyze xenobiotic metabolism. Therefore, ABT should serve as a useful probe for further characterization of adrenal xenobiotic-metabolizing P450 isozymes.
开展了多项研究以确定一种细胞色素P450自杀性抑制剂1-氨基苯并三唑（ABT）对肾上腺类固醇及外源性物质代谢的影响。用ABT与一个能产生NADPH的系统孵育豚鼠肾上腺微粒体，导致总细胞色素P450浓度随时间下降。细胞色素P450水平的最大降幅约为35%，同时血红素含量等摩尔下降。蛋白质免疫印迹分析表明ABT对细胞色素P450脱辅基蛋白水平没有影响。用ABT进行微粒体孵育几乎完全抑制了苄非他明（BZ）N-脱甲基酶和苯并[a]芘（BP）羟化酶的活性。相比之下，ABT对类固醇17α-羟化酶和21-羟化酶的活性均无影响。肾上腺微粒体中类固醇诱导的I型光谱变化也不受ABT影响，而BZ诱导的该变化则被消除。对肾上腺线粒体进行的类似研究表明，ABT对线粒体细胞色素P450浓度或线粒体类固醇代谢没有影响。结果表明，ABT在体外对肾上腺细胞色素P450的作用对催化外源性物质代谢的那些同工酶具有高度选择性。因此，ABT应可作为进一步鉴定肾上腺外源性物质代谢细胞色素P450同工酶的有用探针。
