Contribution of OATP2 (OATP1B1) and OATP8 (OATP1B3) to the hepatic uptake of pitavastatin in humans
Contribution of OATP2 (OATP1B1) and OATP8 (OATP1B3) to the hepatic uptake of pitavastatin in humans
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DOI：
10.1124/jpet.104.068056
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发表时间：
2004-10-01
影响因子：
3.5
通讯作者：
Sugiyama, Y
中科院分区：
文献类型：
--
作者：
Hirano, M;Maeda, K;Sugiyama, Y
Pitavastatin 是一种新型有效的 3-羟甲基戊二酰辅酶 A 还原酶抑制剂，选择性分布到大鼠的肝脏。然而，匹伐他汀的肝脏摄取机制尚未阐明。在本研究中，我们使用表达转运蛋白的 HEK293 细胞和人冻存肝细胞研究了有机阴离子转运多肽 2 (OATP2/OATP1B1) 和 OATP8 (OATP1B3) 对匹伐他汀摄取的贡献。使用表达 OATP2 和 OATP8 的细胞进行的摄取研究表明，OATP2 和 OATP8 的 K-m 值分别为 3.0 和 3.3 muM，可饱和且不依赖 Na+ 的摄取。为了确定哪种转运蛋白对其肝脏摄取更重要，我们提出了一种方法，通过比较匹伐他汀与参考化合物（表达系统和人肝细胞中OATP2（雌酮-3-硫酸酯）和OATP8（胆囊收缩素八肽）的选择性底物）的摄取清除率来估计其对总体肝脏摄取的定量贡献。该方法的概念类似于通常用于估计的所谓相对活性因子方法。将这种方法应用于匹伐他汀，观察到的人肝细胞中的摄取清除率几乎完全由 OATP2 和 OATP8 解释，并且 OATP2 可以解释约 90% 的总肝脏清除率。通过蛋白质印迹分析估计表达系统和肝细胞中每种转运蛋白的相对表达水平也支持了这一结果。用于人类肝脏摄取匹伐他汀。
Pitavastatin, a novel potent 3-hydroxymethylglutaryl-CoA reductase inhibitor, is selectively distributed to the liver in rats. However, the hepatic uptake mechanism of pitavastatin has not been clarified yet. In the present study, we investigated the contribution of organic anion transporting polypeptide 2 (OATP2/OATP1B1) and OATP8 (OATP1B3) to pitavastatin uptake using transporter-expressing HEK293 cells and human cryopreserved hepatocytes. Uptake studies using OATP2- and OATP8-expressing cells revealed a saturable and Na+-independent uptake, with K-m values of 3.0 and 3.3 muM for OATP2 and OATP8, respectively. To determine which transporter is more important for its hepatic uptake, we proposed a methodology for estimating their quantitative contribution to the overall hepatic uptake by comparing the uptake clearance of pitavastatin with that of reference compounds (a selective substrate for OATP2 (estrone-3-sulfate) and OATP8 (cholecystokinin octapeptide) in expression systems and human hepatocytes. The concept of this method is similar to the so-called relative activity factor method often used in estimating the contribution of each cytochrome P450 isoform to the overall metabolism. Applying this method to pitavastatin, the observed uptake clearance in human hepatocytes could be almost completely accounted for by OATP2 and OATP8, and about 90% of the total hepatic clearance could be accounted for by OATP2. This result was also supported by estimating the relative expression level of each transporter in expression systems and hepatocytes by Western blot analysis. These results suggest that OATP2 is the most important transporter for the hepatic uptake of pitavastatin in humans.