Cook Chyung S, Berry Loren M, Kim David H, Burton Earl G, Hribar Jeremy D, Zhang Liming
Pharmacia Corporation, Skokie, Illinois 60077, USA.
Drug Metab Dispos. 2002 Dec;30(12):1344-51. doi: 10.1124/dmd.30.12.1344.
In vitro studies were conducted to identify the major metabolites of eplerenone (EP) and the cytochrome p450 (p450) isozymes involved in its primary oxidative metabolism in humans and dogs. The major in vitro metabolites were identified as 6 beta-hydroxy EP and 21-hydroxy EP in both humans and dogs. EP was metabolized by cDNA-expressed human CYP3A4 and dog CYP3A12 but only minimally by human CYP3A5. In human microsomes, inhibition of total metabolism by the CYP3A-selective inhibitors ketoconazole, troleandomycin, and 6',7'-dihydroxybergamottin, each at 10 micro M concentration, was 83 to 95%, whereas inhibition with inhibitors selective for other p450 isozymes was minimal. In dog liver microsomes, the percentages of inhibition were 53 to 76% with the CYP3A-selective inhibitors. A monoclonal anti-CYP3A4 antibody inhibited EP metabolism by 84%, whereas other monoclonal antibodies had minimal effects. The formation of 6 beta-hydroxy and 21-hydroxy metabolites in human liver microsomes was best correlated with CYP3A-selective dextromethorphan N-demethylation and testosterone 6 beta-hydroxylation activities. EP moderately inhibited only CYP3A (testosterone 6 beta-hydroxylase) activity in human liver microsomes by 23, 34 and 45% at concentrations of 30, 100, and 300 micro M, respectively. With human microsomes, the V(max) and K(m) for 6 beta-hydroxylation and 21-hydroxylation were 0.973 nmol/min/mg and 217 micro M, and 0.143 nmol/min/mg and 211 micro M, respectively. The human hepatic clearance calculated from total in vitro EP metabolism was 2.30 ml/min/kg, which agrees with in vivo data. In conclusion, 6 beta- and 21-hydroxylation of EP is primarily catalyzed by CYP3A4 in humans and CYP3A12 in dogs. Also, it is unlikely that EP would substantially inhibit the metabolism of other drugs that are metabolized by CYP3A4 or other p450 isoforms.
进行了体外研究，以确定依普利酮（EP）的主要代谢产物以及参与其在人和狗体内主要氧化代谢的细胞色素P450（P450）同工酶。在人和狗体内，主要的体外代谢产物均被鉴定为6β-羟基依普利酮和21-羟基依普利酮。依普利酮可被cDNA表达的人CYP3A4和狗CYP3A12代谢，但仅被人CYP3A5少量代谢。在人微粒体中，10μM浓度的CYP3A选择性抑制剂酮康唑、醋竹桃霉素和6',7'-二羟基佛手柑内酯对总代谢的抑制率为83%至95%，而对其他P450同工酶具有选择性的抑制剂的抑制作用则很小。在狗肝微粒体中，CYP3A选择性抑制剂的抑制率为53%至76%。一种单克隆抗CYP3A4抗体对依普利酮代谢的抑制率为84%，而其他单克隆抗体的作用很小。人肝微粒体中6β-羟基和21-羟基代谢产物的形成与CYP3A选择性右美沙芬N-脱甲基化和睾酮6β-羟基化活性的相关性最好。依普利酮在人肝微粒体中仅对CYP3A（睾酮6β-羟化酶）活性有中度抑制作用，在30、100和300μM浓度下的抑制率分别为23%、34%和45%。对于人微粒体，6β-羟基化和21-羟基化的V(max)和K(m)分别为0.973nmol/min/mg和217μM，以及0.143nmol/min/mg和211μM。根据体外依普利酮总代谢计算的人肝清除率为2.30ml/min/kg，这与体内数据一致。总之，依普利酮的6β-和21-羟基化在人体内主要由CYP3A4催化，在狗体内主要由CYP3A12催化。此外，依普利酮不太可能显著抑制由CYP3A4或其他P450同工型代谢的其他药物的代谢。
