Department of Pharmacobiochemistry, Institute of Biomolecular Chemistry, Chemical Research Center of HAS, Budapest, Hungary.
Toxicol Sci. 2010 May;115(1):80-8. doi: 10.1093/toxsci/kfq044. Epub 2010 Feb 10.
Intrahepatic bile acid accumulation due to inhibition of the bile salt export pump (BSEP) has been proposed as a mechanism for drug-induced cholestasis. Many cholestatic drugs do not initiate hepatotoxicity in rats, although they inhibit rat Bsep and cause elevated serum bile acid concentration. In this study, we examined changes in the taurocholate (TC) transport in response to cholestatic drug treatments in human and rat sandwich-cultured hepatocytes. Our experimental setup allows studying the basolateral and canalicular efflux simultaneously, thus comparing drug-induced changes in the vectorial efflux of TC. We found that TC elimination highly differs in human and rat hepatocytes. In human hepatocytes, an equal fraction of TC(uptake) was eliminated by basolateral (34.8%) and canalicular (34.4%) transporters and remained in the cells (30.5%), while in the case of rats, the basolateral transport was dominant (71.7%) and intracellular TC accumulation was negligible (6.9%). The inhibition of BSEP/Bsep resulted in significantly higher intracellular TC(conc) in humans than in rats. The 15-fold difference in intracellular TC(conc) of control in human versus rat hepatocytes was increased 25-fold by troglitazone treatment. MK571 and indomethacin decreased the basolateral efflux and significantly increased the intracellular TC(conc) in rats. In rat hepatocytes, the highest intracellular TC(conc) was observed with cyclosporine A and glibenclamide, which inhibited TC elimination in both directions. Nevertheless, the basolateral transport remained dominant. We conclude that in rats, the higher rate of basolateral bile salt efflux represents an additional protective mechanism in cholestasis, which contributes to species differences in response to hepatotoxic drugs.
由于胆汁盐输出泵 (BSEP) 的抑制导致的肝内胆汁酸积累被认为是药物性胆汁淤积的一种机制。许多胆汁淤积药物在大鼠中不会引起肝毒性，尽管它们抑制大鼠 Bsep 并导致血清胆汁酸浓度升高。在这项研究中，我们检查了在人源和大鼠三明治培养肝细胞中，胆汁淤积药物治疗对牛磺胆酸 (TC) 转运的影响。我们的实验设置允许同时研究基底外侧和管腔侧的流出，从而比较药物诱导的 TC 向量流出变化。我们发现 TC 消除在人和大鼠肝细胞中差异很大。在人肝细胞中，TC(摄取)的相等部分被基底外侧 (34.8%) 和管腔侧 (34.4%) 转运体消除，并留在细胞内 (30.5%)，而在大鼠中，基底外侧转运体占主导地位 (71.7%)，细胞内 TC 积累可以忽略不计 (6.9%)。BSEP/Bsep 的抑制导致人源细胞内 TC(浓度)显著高于大鼠。人源肝细胞中对照组的细胞内 TC(浓度)与大鼠相比相差 15 倍，经曲格列酮处理后增加了 25 倍。MK571 和吲哚美辛降低了基底外侧流出，显著增加了大鼠细胞内 TC(浓度)。在大鼠肝细胞中，环孢素 A 和格列本脲观察到最高的细胞内 TC(浓度)，它们抑制了 TC 在两个方向上的消除。然而，基底外侧转运体仍然占主导地位。我们得出结论，在大鼠中，基底外侧胆汁盐流出率的增加代表了胆汁淤积的另一种保护机制，这导致了对肝毒性药物的物种差异反应。
