Lee A J, Kosh J W, Conney A H, Zhu B T
Department of Basic Pharmaceutical Sciences, College of Pharmacy, University of South Carolina, Columbia, South Carolina.
J Pharmacol Exp Ther. 2001 Aug;298(2):420-32.
We characterized the NADPH-dependent metabolism of 17beta-estradiol (E2) by liver microsomes from 21 male and 12 female human subjects. A large number of radioactive estrogen metabolite peaks were detected following incubations of [3H]E2 with male or female human liver microsomes in the presence of NADPH. The structures of 18 hydroxylated or keto estrogen metabolites formed by these microsomes were identified by gas chromatography/mass spectrometry analysis. 2-Hydroxylation (the formation of 2-OH-E2 and 2-OH-E1) was the dominant metabolic pathway with all human liver microsomes tested. The average ratio of 4-OH-E2 to 2-OH-E2 formation was approximately 1:6. A new monohydroxylated E2 metabolite (chemical structure unidentified) was found to be one of the major metabolites formed by human liver microsomes of both genders. 6beta-OH-E2 and 16beta-OH-E2 were also formed in significant quantities, but products of estrogen 16alpha-hydroxylation (16alpha-OH-E2 + 16alpha-OH-E1) were quantitatively minor metabolites. In addition, many other estrogen metabolites such as 6-keto-E2, 6alpha-OH-E2, 7alpha-OH-E2, 12beta-OH-E2, 15alpha-OH-E2, 15beta-OH-E2, 16beta-OH-E1, and 16-keto-E2 were also formed in relatively small quantities. The overall profiles for the E2 metabolites formed by male and female human liver microsomes were similar, and their average rates were not significantly different. The activity of testosterone 6beta-hydroxylation (a selective probe for CYP3A4/5 activity) strongly correlated with the rate of formation of 2-OH-E2, 4-OH-E2, and several other hydroxyestrogen metabolites by both male and female liver microsomes. The dominant role of hepatic CYP3A4 and CYP3A5 in the formation of these hydroxyestrogen metabolites was further confirmed by incubations of selectively expressed human CYP3A4 or CYP3A5 with [3H]E2 and NADPH.
我们对来自21名男性和12名女性人类受试者的肝脏微粒体中17β-雌二醇（E2）的NADPH依赖性代谢进行了表征。在NADPH存在的情况下，将[3H]E2与男性或女性人类肝脏微粒体一起孵育后，检测到大量放射性雌激素代谢物峰。通过气相色谱/质谱分析鉴定了这些微粒体形成的18种羟基化或酮基雌激素代谢物的结构。2-羟基化（2-OH-E2和2-OH-E1的形成）是所有测试的人类肝脏微粒体的主要代谢途径。4-OH-E2与2-OH-E2形成的平均比率约为1:6。发现一种新的单羟基化E2代谢物（化学结构未鉴定）是两性人类肝脏微粒体形成的主要代谢物之一。6β-OH-E2和16β-OH-E2也大量形成，但雌激素16α-羟基化产物（16α-OH-E2 + 16α-OH-E1）是定量次要代谢物。此外，还形成了许多其他雌激素代谢物，如6-酮-E2、6α-OH-E2、7α-OH-E2、12β-OH-E2、15α-OH-E2、15β-OH-E2、16β-OH-E1和16-酮-E2，但其量相对较少。男性和女性人类肝脏微粒体形成的E2代谢物的总体概况相似，其平均速率没有显著差异。睾酮6β-羟基化活性（CYP3A4/5活性的选择性探针）与男性和女性肝脏微粒体形成2-OH-E2、4-OH-E2和其他几种羟基雌激素代谢物的速率密切相关。通过将选择性表达的人类CYP3A4或CYP3A5与[3H]E2和NADPH一起孵育，进一步证实了肝脏CYP3A4和CYP3A5在这些羟基雌激素代谢物形成中的主导作用。
