Shoji Takahiro, Suzuki Hiroshi, Kusuhara Hiroyuki, Watanabe Yuka, Sakamoto Shingo, Sugiyama Yuichi
Dept. of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The Univ. of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Am J Physiol Gastrointest Liver Physiol. 2004 Oct;287(4):G749-56. doi: 10.1152/ajpgi.00065.2003. Epub 2004 Jun 24.
The mechanism for the cellular extrusion of organic anions across the intestinal basolateral membrane was examined using isolated membrane vesicles from rat jejunum, ileum, and colon. It was found that 17beta-estradiol 17beta-D-glucuronide (E217betaG) is taken up in an ATP-dependent manner into the basolateral membrane vesicles (BLMVs) but not into the brush-border or microsomal counterparts. The ATP-dependent uptake of E217betaG into BLMVs from jejunum and ileum was described by a single component with a Km value of 23.5 and 8.31 microM, respectively, whereas that into the BLMVs from colon was described by assuming the presence of high (Km=0.82 microM)- and low-affinity (Km=35.4 microM) components. Taurocholate, 6-hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole glucuronide and taurolithocholate sulfate, but not leukotriene C4, were significantly taken up by the BLMVs. In addition to such substrate specificity, the inhibitor sensitivity of the ATP-dependent transport in BLMVs was similar to that of rat multidrug resistance-associated protein 3 (Mrp3), which is located on the basolateral membrane of enterocytes. Together with the fact that the rank order of the extent of the expression of Mrp3 (jejunum < ileum << colon) is in parallel with that of the extent of the transport of ligands, these results suggest that the ATP-dependent uptake of organic anions into isolated intestinal BLMVs is at least partly mediated by Mrp3.
利用大鼠空肠、回肠和结肠分离的膜囊泡，研究了有机阴离子跨肠基底外侧膜进行细胞外排的机制。研究发现，17β-雌二醇17β-D-葡萄糖醛酸苷（E217βG）以ATP依赖的方式被摄取到基底外侧膜囊泡（BLMVs）中，但不被摄取到刷状缘或微粒体对应物中。空肠和回肠BLMVs对E217βG的ATP依赖摄取分别由一个Km值为23.5和8.31 microM的单一成分描述，而结肠BLMVs对E217βG的摄取则通过假设存在高亲和力（Km = 0.82 microM）和低亲和力（Km = 35.4 microM）成分来描述。牛磺胆酸盐、6-羟基-5,7-二甲基-2-甲基氨基-4-(3-吡啶甲基)苯并噻唑葡萄糖醛酸苷和牛磺石胆酸硫酸盐，但不是白三烯C4，被BLMVs显著摄取。除了这种底物特异性外，BLMVs中ATP依赖转运的抑制剂敏感性与位于肠上皮细胞基底外侧膜上的大鼠多药耐药相关蛋白3（Mrp3）相似。再加上Mrp3表达程度的排序（空肠<回肠<<结肠）与配体转运程度的排序平行这一事实，这些结果表明，有机阴离子对分离的肠BLMVs的ATP依赖摄取至少部分由Mrp3介导。
