Ishizuka H, Konno K, Naganuma H, Nishimura K, Kouzuki H, Suzuki H, Stieger B, Meier P J, Sugiyama Y
Analytical and Metabolic Research Laboratories, Sankyo Co., Ltd., Shinagawa-ku, Tokyo 140, Japan.
J Pharmacol Exp Ther. 1998 Oct;287(1):37-42.
The mechanism for hepatic uptake of temocaprilat, an angiotensin-converting enzyme inhibitor that is predominantly excreted into bile was studied using isolated rat hepatocytes and COS-7 cells expressing the organic anion transporting polypeptide (oatp1). The uptake of temocaprilat into isolated rat hepatocytes exhibited saturation with a Km of 20.9 microM and a Vmax of 0.21 nmol/min/mg protein. This uptake was temperature sensitive and was significantly reduced by metabolic inhibitors, a sulfhydryl-modifying reagent and an anion-exchange inhibitor, although the replacement of Na+ with Li+ in the medium did not affect the uptake. [3H]Temocaprilat uptake was inhibited by estradiol-17beta-D-glucuronide and dibromosulphophthalein, typical substrates for the Na+-independent organic anion transporter, in a concentration-dependent manner, whereas excess estradiol-17beta-D-glucuronide did not completely inhibit the uptake. Temocaprilat uptake into COS-7 cells transfected with oatp1 cDNA revealed a concentration-dependency with a Km of 46.7 microM, a value comparable with that obtained in isolated hepatocytes. The contribution of oatp1 to carrier-mediated hepatic uptake of temocaprilat was less than 50% by correcting the uptake clearance with that of estradiol-17beta-D-glucuronide. A good linear correlation was observed for the inhibitory effect of angiotensin-converting enzyme inhibitors (benazeprilat, cilazaprilat, delaprilat and enalaprilat) between isolated hepatocytes and oatp1-expressing cells. These data suggest that oatp1, along with another transporter(s), mediates the uptake of angiotensin-converting enzyme inhibitors into rat hepatocytes.
使用分离的大鼠肝细胞和表达有机阴离子转运多肽（oatp1）的COS-7细胞，研究了替莫卡普利拉（一种主要经胆汁排泄的血管紧张素转换酶抑制剂）的肝脏摄取机制。替莫卡普利拉在分离的大鼠肝细胞中的摄取呈现饱和状态，Km为20.9微摩尔，Vmax为0.21纳摩尔/分钟/毫克蛋白。这种摄取对温度敏感，并且被代谢抑制剂、巯基修饰试剂和阴离子交换抑制剂显著降低，尽管培养基中用Li⁺替代Na⁺并不影响摄取。[³H]替莫卡普利拉的摄取被雌二醇-17β-D-葡萄糖醛酸苷和二溴磺酞钠（Na⁺非依赖性有机阴离子转运体的典型底物）以浓度依赖性方式抑制，而过量的雌二醇-17β-D-葡萄糖醛酸苷并未完全抑制摄取。替莫卡普利拉在转染了oatp1 cDNA的COS-7细胞中的摄取显示出浓度依赖性，Km为46.7微摩尔，该值与在分离的肝细胞中获得的值相当。通过用雌二醇-17β-D-葡萄糖醛酸苷的摄取清除率校正摄取清除率，oatp1对载体介导的替莫卡普利拉肝脏摄取的贡献小于50%。在分离的肝细胞和表达oatp1的细胞之间，观察到血管紧张素转换酶抑制剂（贝那普利拉、西拉普利拉、地拉普利拉和依那普利拉）的抑制作用具有良好的线性相关性。这些数据表明，oatp1与另一种转运体共同介导血管紧张素转换酶抑制剂进入大鼠肝细胞。
