苯巴比妥诱导对普萘洛尔对映体的体外葡醛酸缀合反应立体选择性的影响

Influence of Phenobarbital Induction on the Stereoselectivity of Propranolol Glucuronidation in Rat Hepatic Microsome

目的：探讨苯巴比妥诱导作用对鼠肝微粒体的体外葡醛酸结合反应立体选择性的影响。方法：用空白对照微粒体和经苯巴比妥（ＰＢ）诱导的微粒体作酶源，用ＵＤＰＧＡ启动葡醛酸结合反应，ＲＰ－ＨＰＬＣ法测定温育液中底物的浓度，观察苯巴比妥诱导作用对普萘洛尔对映体葡醛酸结合反应的立体选择性的影响。结果：普萘洛尔Ｒ（＋ ）和Ｓ（－ ）两种对映体在两种鼠肝微粒体的体外孵育葡醛酸缀合代谢中，酶与底物亲和力、最大反应速度和内在清除率均表现出立体选择性。在酶与底物的亲和性和Ｃｌｉｎｔ参数方面，Ｓ（－ ）为优势对映体。诱导剂ＰＢ的处理使酶与Ｓ（－ ）对映体的亲和力和最大反应速度均显著增强，与Ｒ（＋ ）对映体的最大反应速度显著增强，但酶与Ｒ（＋ ）对映体的亲和力无显著变化，Ｓ（－ ）对映体的Ｃｌｉｎｔ值显著下降，而Ｒ（＋ ）对映体的Ｃｌｉｎｔ值则显著增大。酶源对普萘洛尔对映体的葡萄糖醛酸化清除能力以Ｓ（－ ）型为优势对映体。结论：ＰＢ的诱导使鼠肝微粒体立体选择性差异缩小，但未改变其顺序，仍以Ｓ（－ ）型对映体占优势。

Objective:To compare the glucuronidation stereoselectivities of propranolol in rat hepatic microsome and study the influence of inducer PB on the glucuronidation of propranolol enantiomers.Methods:Rat hepatic microsome from control and PB induced rats were prepared for glucuronidation reaction.A RP HPLC method was used to determine propranolol concentrations in microsome incubations.Results:Stereoselectivities were observed in enzymatic affinity(Km),maximum reaction speed(Vmax) and intrinsic clearance (Clint).PB induction singnificantly increased Vmax and Clint of R(+) propranolol( P <0.01 or 0.001),and Km and Vmax of S(-)propranolol( P <0.001);but Clint of S(-) propranolol was significantly lowed( P <0.05).The glucuronidation of propranolol in rat hepatic microsome has stereoselectivity of S(-) propranolol,and the induction of PB reduced the difference between R(+) and S(-) propranolol glucuronidation in rat hepatic microsome.Conclusion:The PB induction changed the catalysis abilities of rat hepatic microsome to propranolol glucuronidation and still remained the stereoselectivity of S(-) propranolol.