In vitro proguanil activation to cycloguanil is mediated by CYP2C19 and CYP3A4 in adult Chinese liver microsomes^1  

体外中国成人肝微粒体中氯胍活化为氯胍三嗪由CYP2C19和CYP3A4介导(英文)

作　　者：卢爱华[1] 舒焱[1] 黄松林[1] 王伟[1] 欧阳冬生[1] 周宏灏[1] 

机构地区：[1]湖南医科大学遗传药理学研究室,长沙中国410078

出　　处：《Acta Pharmacologica Sinica》2000年第8期78-83,共6页中国药理学报（英文版）

基　　金：Project supported by the National Natural Science Foundation of China, № F39330230, and by China Medical Board of America, № 92-568 and 99-697.

摘　　要：To identify the cytochrome P450 isoforms involved in proguanil (PG) activation to cycloguanil (CG) in Chinese liver microsomes. METHODS: The kinetics of the CG formation from PG was determined in the liver microsomes of 6 Chinese subjects. Selective chemical inhibitors to various cytochrome P450 isoforms were employed to conduct inhibition experiments. The relationship between the CG formation and S-mephenytoin 4'-hy-droxylation was analyzed. RESULTS: The kinetic behaviors of CG formation were described well by a single-enzyme Michaelis-Menten equation in five livers. The apparent Km and Vmax were (82±47) μmol·L-1 and (8±6)pmol·min-1·mg-1 protein, respectively. However, the remaining one displayed a two-enzyme kinetic behavior. Inhibition experiments showed that trolean-domycin (100 μmol·L-1) and diethyldithiocarbamate (100μmol·L-1), as potent CYP3A4 and CYP2E1 inhibitors, respectively, reduced the formation rate of CG by 81.1 % and 47.23 % , while quinidine (10 μmol·L-1), furafylline (20 μmol·L-1), and sulfaphenazole (10μmol·L-1), which were inhibitors towards CYP2D6, 1A2 and 2C9/10, respectively, did not display significant inhibition. At a low PG concentration of 5 μmol·L-1, the CG formation correlated well with S-mephenytoin 4'-hydroxylation ( r= 0.805, P < 0.05). Nevertheless, when a high substrate concentration (500μmol·L-1) was used, the correlation coefficient decreased(r=0.581, P<0.05). CONCLUSION: The present study indicates that CYP3A4 and CYP2C19 are involved in PG activation to CG in adult Chinese liver microsomes. CYP2C19 played an important role in the clearance of PG at a substrate concentration close to in vivo therapeutic concentrations, while CYP3A4 gradually made a dominant contribution with the increase of PG concentration.目的:鉴定中国成人肝微粒体中介导氯胍(PG)活化为氯胍三嗪(CG)的细胞色素P450(CYP450).方法:分析中国成人(n=6)肝微粒体中PG活化为CG的酶促动力学,各种CYP450抑制剂对该代谢的作用及其与S-美芬妥英4′-羟化的关系.结果:6个标本中,除一个外(两酶米氏模型),PG活化为CG的酶促动力学符合米氏一酶模型;CYP3A4和CYP2E1的选择性抑制剂醋竹桃霉素(81.1％)和二乙二硫基苯甲酸(47.23％)可抑制CG生成,其它抑制剂没有明显作用;在低PG浓度时,PG的环化与S-美芬妥英4′-羟化显著相关(r=0.805,P<0.05),高浓度时相关性明显减小.结论:在中国成人肝微粒体中CYP2C19和CYP3A4参与了PG活化为CG.

关 键 词：ANTIMALARIALS metabolism cytochrome P-450 CYP2C19 cytochrome P-450 CYP3A4 enzyme inhibitiors MEPHENYTOIN 

分 类 号：R96[医药卫生—药理学]