Ishiguro Naoki, Maeda Kazuya, Kishimoto Wataru, Saito Asami, Harada Akiko, Ebner Thomas, Roth Willy, Igarashi Takashi, Sugiyama Yuichi
Department of Pharmacokinetics and Non-Clinical Safety, Kawanishi Pharma Research Institute, Nippon Boehringer Ingelheim Co., Ltd., Hyogo, Japan.
Drug Metab Dispos. 2006 Jul;34(7):1109-15. doi: 10.1124/dmd.105.009175. Epub 2006 Apr 12.
Telmisartan, a nonpeptide angiotensin II receptor antagonist, is selectively distributed to liver. In the present study, we have characterized the contribution of organic anion transporting polypeptide (OATP) isoforms to the hepatic uptake of telmisartan by isolated rat hepatocytes, human cryopreserved hepatocytes, and human transporter-expressing cells. Because it is difficult to evaluate the transport activity of telmisartan because of its extensive adsorption to cells and culture materials, we performed the uptake study in the presence of human serum albumin. The saturable uptake of telmisartan into isolated rat hepatocytes took place in a Na(+)-independent manner and was inhibited by pravastatin, taurocholate, and digoxin, which are Oatp substrates and inhibitors, but not by organic cation, tetraethylammonium, indicating the involvement of Oatp isoforms in its uptake into rat hepatocytes. To identify which human OATP transporters are important for the hepatic uptake of telmisartan, the uptake assay was carried out using OATP1B1- and OATP1B3-expressing human embryonic kidney 293 cells and cryopreserved human hepatocytes. The uptake of telmisartan by OATP1B3-expressing cells was saturable (K(m) = 0.81 microM) and significantly higher than that by vector-transfected cells. In contrast, no significant uptake was observed in OATP1B1-expressing cells. We also observed the saturable uptake of telmisartan by human hepatocytes. Thirty micromolar estrone-3-sulfate, which can selectively inhibit OATP1B1-mediated uptake compared with OATP1B3, did not inhibit the uptake of telmisartan in human hepatocytes, whereas it could inhibit the uptake of estradiol 17beta-d-glucuronide mediated by OATP1B1. These results suggest that OATP1B3 is predominantly involved in the hepatic uptake of telmisartan in humans.
替米沙坦是一种非肽类血管紧张素II受体拮抗剂，可选择性地分布于肝脏。在本研究中，我们通过分离的大鼠肝细胞、人冻存肝细胞和表达人转运蛋白的细胞，对有机阴离子转运多肽（OATP）亚型在替米沙坦肝脏摄取中的作用进行了表征。由于替米沙坦对细胞和培养材料有广泛吸附，难以评估其转运活性，因此我们在人血清白蛋白存在的情况下进行了摄取研究。替米沙坦在分离的大鼠肝细胞中的饱和摄取以不依赖Na(+)的方式发生，并受到普伐他汀、牛磺胆酸盐和地高辛的抑制，这些都是Oatp底物和抑制剂，但不受有机阳离子四乙铵的抑制，这表明Oatp亚型参与了其进入大鼠肝细胞的过程。为了确定哪些人OATP转运蛋白对替米沙坦的肝脏摄取很重要，我们使用表达OATP1B1和OATP1B3的人胚肾293细胞以及冻存的人肝细胞进行了摄取试验。表达OATP1B3的细胞对替米沙坦的摄取是饱和的（K(m)=0.81 microM），且显著高于载体转染细胞。相比之下，在表达OATP1B1的细胞中未观察到明显摄取。我们还观察到替米沙坦在人肝细胞中的饱和摄取。与OATP1B3相比，30微摩尔的硫酸雌酮-3-酯可选择性抑制OATP1B1介导的摄取，但不抑制人肝细胞中替米沙坦的摄取，而它可以抑制OATP1B1介导的17β-d-葡萄糖醛酸雌二醇的摄取。这些结果表明，OATP1B3在人类替米沙坦的肝脏摄取中起主要作用。
