红细胞、血浆蛋白及溶酶体对汉防己甲素和汉防己乙素系统暴露的影响

目的：汉防己为防己科植物粉防己（Stephania tetrandra S. Moore）的干燥根。汉防己甲素和汉防己乙素是其两个主要成分，具有抗肿瘤等多方面药效活性。为了帮助进一步考察汉防己甲素和汉防己乙素的药效作用，我们对两个双苄基异喹啉类生物碱开展了大鼠和体外药代研究。方法：大鼠口服或静脉给药汉防己提取物、汉防己甲素或汉防己乙素单体化合物以阐明汉防己甲素和汉防己乙素的药代动力学特征；在体外检测汉防己甲素和汉防己乙素的血浆蛋白结合、全血-血浆分配、溶酶体捕获。以上实验产生的生物样品均采用液质联用技术进行分析。结果：研究发现汉防己甲素和汉防己乙素有两个药代特征，其一是这两个化合物的全血系统暴露水平均高于其各自血浆系统暴露水平，其二是在相同的给药剂量、动物实验条件及分析检测条件下，两个化合物在灌胃汉防己水提物后的系统暴露水平均高于其各自在灌胃单个化合物后的暴露水平。汉防己甲素和汉防己乙素的大鼠血浆游离药物分数约为2%～5%，其在大鼠红细胞浓度比在大鼠血浆浓度高5倍左右。溶酶体抑制剂阻碍溶酶体捕获这两个化合物并显著减少其在HEK-293细胞中浓度。 结论：血浆蛋白结合、红细胞结合及组织细胞中溶酶体捕获三个因素极大地限制了游离的汉防己甲素和汉防己乙素的系统暴露水平，该药代特点应在围绕这两个中药化合物开展药效研究时关注。

Effect of erythrocytes,plasma proteins,and lysosomes on systemic exposure to tetrandrine and fangchinoline

AIM: The Chinese medicinal herb Hanfangji is dried roots of Stephania tetrandra S. Moore (Family, Menispermaceae). Tetrandrine and fangchinoline are two major constituents of Hanfangji and these bisbenzyltetrahydroisoquinoline alkaloids possess anti-cancer and other pharmacological activities. To facilitate further pharmacodynamic investigation of these compounds, a pharmacokinetic investigation was performed in rats and in vitro. METHODS: Pharmacokinetics of tetrandrine and fangchinoline were characterized in rats p.o. or i.v. dosing an aqueous extract of Hanfangji or the individual compound. Unbound levels of systemic exposure to these two alkaloids were assessed using in vitro studies of plasma protein binding, blood-plasma partition, and lysosomal trapping. All the study samples were analyzed by liquid chromatography/mass spectrometry.RESULTS: We found two pharmacokinetic features of tetrandrine and fangchinoline. First, the two compounds had blood levels of systemic exposure substantially higher than the respective plasma levels of systemic exposure. Second, the two compounds exhibited significantly higher systemic exposure levels after p.o. dosing an aqueous extract of Hanfangji than the respective exposure levels after p.o. dosing the individual compound, at the same compound dose levels and under the same conditions for analytical measurement and the same conditions for animal study. Unbound fractions of tetrandrine and fangchinoline in rat plasma were 2%-5%and the concentrations of the alkaloids in rat erythrocytes were 5-times higher than those in rat plasma. Lysosomal inhibitor could block their trapping in lysosomes and significantly reduce their concentrations in HEK-293 cells. CONCLUSION: The following pharmacokinetic aspects should be noted in pharmacodynamic investigation of tetrandrine and fangchinoline: extensive binding with plasma proteins, extensive binding with erythrocytes, and trapping by lysosomes of tissue cells substantially reduce the levels of unbound tetrandrine and fangchinoline in the systemic circulation.