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Prediction of hepatobiliary transport of drugs : Contribution of carrier-mediated transport in the detoxication of xenobiotics

药物肝胆转运的预测：载体介导的转运在外源物解毒中的贡献

基本信息

批准号：
06402058
负责人：
SUGIYAMA Yuichi
金额：
$ 10.5万
依托单位：
Faculty of Pharmaceutical Sciences, The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

The biliary excretion plays an important role in the detoxication of xenobiotics. In the present study, we clarified the mechanism for the biliary excretion of organic anions including conjugative metabolites in normal SD rats and in Eisaihyper-bilirubinemic rats (EHBR) whose multispecific organic anion transporter on the bile canalicular membrane (cMOAT) is hereditarily defective. ATP-dependent uptake of glutathione conjugate of dinitrophenol and E3040 glucuronide into the isolated bile canalicular membrane vesicles (CMV) was observed only in SD rats, but not in EHBR.In contrast, E3040 sulfate uptake into CMV was not stimulated in the presence of ATP in CMV isolated from both SD and EHBR.These results suggest that glucuronide, but not sulfate, can be the substrate for cMOAT.Furthermore, we examined the molecular feature of cMOAT.We fixed our eyes upon the fact (1) that the substrate specificity of cMOAT resembles that of multidrug resistance associated protein (MRP), a primary active transporter located on the multidrug resistance tumor cells and (2) that a series of the primary active transporters possess conserved ATP-binding cassette (ABC) region, and prepared the degenerated PCR primer for the carboxy-terminal ABC of human MRP.A 421 bp fragment was amplified from the SD rat liver cDNA.Northern blot analysis of poly (A)+RNA from SD rat liver revealed the presence of 5 kb and 8.5kb mRNA species which hybridized to this fragment. In contrast, poly (A)+ RNA from EHBR did not hybridize to this fragment. These results suggest (1) that the impaired expression of this particular region might be related to the pathogenesis of hyperbilirubinemia in EHBR and that this region might encode part of cMOAT.

胆汁排泄在外源性物质的解毒过程中起重要作用。本研究阐明了正常SD大鼠和遗传性胆小管膜多特异性有机阴离子转运体（cMOAT）缺陷的高胆红素血症大鼠（EHBR）胆汁排泄有机阴离子（包括共轭代谢产物）的机制。仅在SD大鼠中观察到二硝基苯酚和E3040葡萄糖醛酸苷的谷胱甘肽结合物进入分离的胆小管膜囊泡（CMV）的ATP依赖性摄取，而在EHBR中未观察到。相反，在SD和EHBR分离的CMV中，存在ATP时，CMV对E3040硫酸盐的摄取不受刺激。这些结果表明，葡萄糖醛酸苷，而不是硫酸盐，可以成为cMOAT的底物。此外，我们研究了cMOAT的分子特征，发现cMOAT的底物特异性与多药耐药相关蛋白（MRP）相似，MRP是多药耐药肿瘤细胞上的主要活性转运蛋白; cMOAT的一系列主要活性转运蛋白具有保守的ATP结合盒（ABC）区，从SD大鼠肝cDNA中扩增出421 bp的片段，用北方印迹法对SD大鼠肝组织中的poly（A）+RNA进行杂交，结果显示与该片段杂交的mRNA分别为5 kb和8.5kb。相反，来自EHBR的poly（A）+ RNA不与该片段杂交。这些结果提示：（1）该区域的表达异常可能与EHBR高胆红素血症的发病机制有关，该区域可能编码cMOAT的一部分。