大黄素在大鼠肝微粒体酶动力学及胡椒碱对其代谢的影响

Metabolic kinetics of emodin and inhibition of emodin glucuronidation by piperine in rat liver microsome

目的分别研究大黄素在雌性和雄性大鼠肝微粒体中酶促动力学及胡椒碱对其代谢的影响。方法将系列浓度的大黄素分别与雌性或雄性大鼠肝微粒体进行体外共孵育,采用HPLC法测定孵育液中大黄素的浓度,并计算酶动力学参数。另将不同浓度的胡椒碱与大黄素在大鼠肝微粒体中进行共孵育,计算胡椒碱对大黄素代谢的抑制常数(Ki),进一步探讨其代谢抑制类型,并推测其对大黄素体内代谢的影响。结果大黄素在雌性和雄性大鼠肝微粒体中代谢的最大反应速率(Vmax)分别为(84.49±9.62)和(32.97±7.37)μmol·min^(-1)·mg protein^(-1),米氏常数(Km)分别为(60.50±8.71)和(34.48±4.96)μmol·L^(-1),内在清除速率(CLint)分别为(1 406±112)和(965±73.7)μL·min^(-1)·mg protein^(-1),雌性和雄性大鼠的Ki值分别为0.35和0.31μmol·L^(-1)。结论大鼠肝微粒体中胡椒碱抑制大黄素的葡萄糖醛酸代谢呈浓度依赖性,根据图形推断其抑制类型为混合性抑制,并推测合用胡椒碱后,大黄素在大鼠体内的血药浓度显著增加,为其进一步开发研究提供了参考依据。

Objective To investigate the enzyme kinetic and the effect of piperine on the metabolism of emodin in female and male rat liver microsome. Methods Various concentrations of emodin were incubated with rat liver microsome,and the rest of emodin in pooled incubation mixture was determined by HPLC to calculate emodin＇s enzyme kinetic parameters The inhibition of UGT-catalyzed emodin glucuronidation by piperine was studied and the inhibition kinetic constant（ Ki）was determined. Meanwhile,the Dixon plot and Cornish-Bowden plot were investigated to infer the inhibition type. And in vitro-in vivo extrapolation was employed to infer potential drug-drug interactions between emodin and piperine. Results In liver microsomes of female and male rats,Vmaxvalues were（84. 49 ± 9. 62） and（32. 97 ± 7. 37） μmol·min^-1·mg protein^-1,Kmwere（60. 50 ± 8. 71） and（ 34. 48 ± 4. 96） μmol·L^-1as well as the CLintvalue were（ 1406 ±112） and（ 965 ± 73. 7） μL·min^-1·mg protein^-1,and Ki were 0. 35 and 0. 31 μmol·L^-1,respectively.Conclusions The piperine shows dose-dependent inhibition towards emodin glucuronidation and the inhibition type fits the mixed model for rat liver microsomes. The concentration of emodin in vivo might sharply enhance,which will provide references for the further research.