Mutual Inhibition between Carvedilol Enantiomers during Racemate Glucuronidation Mediated by Human Liver and Intestinal Microsomes
作者:Yoh Takekuma、Keiji Yagisawa、Mitsuru Sugawara
DOI:10.1248/bpb.35.151
日期:——
Carvedilol is administered orally as a racemic mixture of R(+)- and S(−)-enantiomers for treatment of angina pectoris, hypertension and chronic heart failure. We have reported that enzyme kinetic parameters for carvedilol glucuronidation by human liver microsomes (HLM) differed greatly depending on the substrate form, namely, racemic carvedilol and each enantiomer. These phenomena were thought to be caused by mutual inhibition between carvedilol enantiomers during racemate glucuronidation. The aim of this study was to clarify the mechanism of these phenomena in HLM and human intestinal microsomes (HIM) and its relevance to uridine 5′-diphosphate (UDP)-glucuronosyl transferase (UGT) 1A1, UGT2B4 and UGT2B7, which mainly metabolize carvedilol directly in phase II enzymes. HLM apparently preferred metabolizing (S)-carvedilol to (R)-carvedilol in the racemate, but true activities of HLM for both glucuronidation were approximately equal. By determination of the inhibitory effects of (S)-carvedilol on (R)-carvedilol glucuronidation and vice versa, it was shown that (R)-carvedilol glucuronidation was more easily inhibited than was (S)-carvedilol glucuronidation. UGT2B7 was responsible for (S)-carvedilol glucuronidation in HLM. Ratios of contribution to (R)-carvedilol glucuronidation were approximately equal among UGT1A1, UGT2B4 and UGT2B7. However, enzyme kinetic parameters were different between the two lots of HLM used in this study, depending on the contribution ratio of UGT2B4, in which (R)-glucuronidation was much more easily inhibited by (S)-carvedilol than was (S)-glucuronidation by (R)-carvedilol. Meanwhile, HIM preferred metabolizing (R)-carvedilol, and this tendency was not different between the kinds of substrate form.
卡维地洛以 R(+)- 和 S(-)- 对映异构体的外消旋混合物形式口服,用于治疗心绞痛、高血压和慢性心力衰竭。我们曾报道,人肝微粒体(HLM)对卡维地洛葡萄糖醛酸化作用的酶动力学参数因底物形式(即外消旋卡维地洛和每种对映体)的不同而有很大差异。这些现象被认为是外消旋体葡糖醛酸化过程中卡维地洛对映体之间相互抑制所致。本研究的目的是阐明这些现象在 HLM 和人肠道微粒体(HIM)中的机制及其与尿苷-5′-二磷酸(UDP)-葡萄糖醛酸转移酶(UGT)1A1、UGT2B4 和 UGT2B7 的相关性,它们主要在第二阶段酶中直接代谢卡维地洛。HLM 显然更倾向于代谢外消旋体中的(S)-卡维地洛,而不是(R)-卡维地洛,但 HLM 对两种葡萄糖醛酸化作用的真实活性大致相同。通过测定(S)-卡维地洛对(R)-卡维地洛葡糖醛酸化的抑制作用和(R)-卡维地洛对(S)-卡维地洛葡糖醛酸化的抑制作用,结果表明(R)-卡维地洛葡糖醛酸化比(S)-卡维地洛葡糖醛酸化更容易受到抑制。UGT2B7 负责(S)-卡维地洛在 HLM 中的葡萄糖醛酸化。UGT1A1 、UGT2B4 和 UGT2B7 对(R)-卡维地洛葡萄糖醛酸化作用的比例大致相同。然而,本研究中使用的两个批次的 HLM 的酶动力学参数有所不同,这取决于 UGT2B4 的贡献比例,其中(R)-葡萄糖醛酸化更容易被(S)-卡维地洛抑制,而(S)-葡萄糖醛酸化更容易被(R)-卡维地洛抑制。同时,HIM 更倾向于代谢 (R)-卡维地洛,而且这种倾向在底物形式的种类之间没有差异。