Kouzuki H, Suzuki H, Stieger B, Meier P J, Sugiyama Y
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
J Pharmacol Exp Ther. 2000 Feb;292(2):505-11.
In the present study, we compared the inhibitory effects of organic anions (including bile acids) on the uptake of taurocholate (TC) and estradiol 17beta-D-glucuronide (E(2)17betaG), typical substrates for sodium taurocholate cotransporting polypeptide (Ntcp) and organic anion transporting polypeptide (oatp1), respectively, using primary cultured rat hepatocytes and Ntcp- or oatp1-transfected COS-7 cells. The Na(+)-dependent uptake of TC was inhibited by nine bile acids and five nonbile acid organic anions in a concentration-dependent manner, and their inhibitory effects were similar in both primary cultured rat hepatocytes and Ntcp-transfected COS-7 cells. BQ-123 (1 microM) and indomethacin (10 microM), both of which exhibit no Ntcp-mediated transport, significantly inhibited the Na(+)-dependent uptake of TC mediated by Ntcp. In addition, the Na(+)-independent uptake of E(2)17betaG was inhibited by 15 organic anions in a concentration-dependent manner, and their inhibitory effects were similar between primary cultured rat hepatocytes and oatp1-transfected COS-7 cells. BQ-123 (1 microM), pravastatin (1 microM), and indomethacin (10 microM), all of which do not undergo oatp1-mediated transport, significantly inhibited the Na(+)-independent uptake of E(2)17betaG mediated by oatp1. These results are consistent with the hypothesis that the hepatic uptake of TC and E(2)17betaG is predominantly mediated by Ntcp and oatp1, respectively. In addition, it was clearly demonstrated that we cannot refer to the substrate specificity of transporters based on inhibition studies.
在本研究中，我们使用原代培养的大鼠肝细胞以及转染了Ntcp或oatp1的COS - 7细胞，比较了有机阴离子（包括胆汁酸）对牛磺胆酸盐（TC）和17β - D - 葡萄糖醛酸雌二醇（E₂17βG）摄取的抑制作用，它们分别是牛磺胆酸钠共转运多肽（Ntcp）和有机阴离子转运多肽（oatp1）的典型底物。TC的Na⁺依赖性摄取受到九种胆汁酸和五种非胆汁酸有机阴离子的浓度依赖性抑制，并且它们在原代培养的大鼠肝细胞和转染Ntcp的COS - 7细胞中的抑制作用相似。BQ - 123（1 μM）和吲哚美辛（10 μM）均不表现出Ntcp介导的转运，但能显著抑制由Ntcp介导的TC的Na⁺依赖性摄取。此外，E₂17βG的Na⁺非依赖性摄取受到15种有机阴离子的浓度依赖性抑制，并且它们在原代培养的大鼠肝细胞和转染oatp1的COS - 7细胞之间的抑制作用相似。BQ - 123（1 μM）、普伐他汀（1 μM）和吲哚美辛（10 μM）均不经历oatp1介导的转运，但能显著抑制由oatp1介导的E₂17βG的Na⁺非依赖性摄取。这些结果与以下假设一致，即肝脏对TC和E₂17βG的摄取分别主要由Ntcp和oatp1介导。此外，清楚地表明我们不能基于抑制研究来推断转运体的底物特异性。
