Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Korea.
Drug Metab Dispos. 2010 Nov;38(11):2007-13. doi: 10.1124/dmd.110.035295. Epub 2010 Aug 16.
Midazolam undergoes oxidative hydroxylation by CYP3A to its metabolites, which are excreted mainly as glucuronidated conjugates into the urine. In this study, we examined the glucuronidation of hydroxymidazolam in human liver microsomes (HLMs) and characterized the UDP-glucuronosyltransferases (UGTs) involved in 1'- and 4-hydroxymidazolam glucuronidation. Among the 12 UGT isoforms tested, the O- and N-glucuronidation of 1'-hydroxymidazolam was mediated by UGT2B4/2B7 and 1A4, respectively. In contrast, the glucuronidation of 4-hydroxymidazolam was mediated by UGT1A4. Consistent with these observations, the UGT1A4 inhibitor hecogenin and the UGT2B7 substrate diclofenac potently inhibited the N- and O-glucuronidation of 1'-hydroxymidazolam in HLMs, respectively. A correlation analysis of UGT enzymatic activity and the formation rate of glucuronide metabolites from 1'- and 4-hydroxymidazolam in 25 HLMs showed that hydroxymidazolam glucuronidation is correlated with UGT1A4-mediated lamotrigine glucuronidation and UGT2B7-mediated diclofenac glucuronidation activity. Taken together, these findings indicate that UGT1A4, 2B4, and 2B7 are major isoforms responsible for glucuronide conjugate formation from 1'- and 4-hydroxymidazolam, which are the two major oxidative metabolites of midazolam.
咪达唑仑经 CYP3A 氧化羟化生成其代谢物，主要以葡萄糖醛酸结合物的形式经尿液排泄。本研究考察了人肝微粒体（HLM）中羟咪达唑仑的葡萄糖醛酸化作用，并对参与 1'-和 4-羟咪达唑仑葡萄糖醛酸化的 UDP-葡糖醛酸基转移酶（UGTs）进行了表征。在测试的 12 种 UGT 同工酶中，1'-羟咪达唑仑的 O-和 N-葡萄糖醛酸化分别由 UGT2B4/2B7 和 1A4 介导。相比之下，4-羟咪达唑仑的葡萄糖醛酸化由 UGT1A4 介导。这些观察结果与 UGT1A4 抑制剂海柯苷元和 UGT2B7 底物双氯芬酸分别对 HLM 中 1'-羟咪达唑仑的 N-和 O-葡萄糖醛酸化的强烈抑制作用一致。对 25 个人 HLM 中 1'-和 4-羟咪达唑仑的 UGT 酶活性与葡萄糖醛酸代谢物形成率的相关分析表明，羟咪达唑仑的葡萄糖醛酸化与 UGT1A4 介导的拉莫三嗪葡萄糖醛酸化和 UGT2B7 介导的双氯芬酸葡萄糖醛酸化活性相关。综上所述，这些发现表明 UGT1A4、2B4 和 2B7 是负责生成 1'-和 4-羟咪达唑仑葡萄糖醛酸结合物的主要同工酶，而 1'-和 4-羟咪达唑仑是咪达唑仑的两种主要氧化代谢物。
