Inhibition of glutathione-conjugate secretion from isolated hepatocytes by dipolar bile acids and other organic anions.
Inhibition of glutathione-conjugate secretion from isolated hepatocytes by dipolar bile acids and other organic anions.
复制标题
偶极胆汁酸和其他有机阴离子抑制离体肝细胞分泌谷胱甘肽结合物。
作者：
R. Elferink;R. Ottenhoff;A. Radominska;A. F. Hofmann;Folkert Kuipers;Plm Jansen
研究了有机化合物光谱对肝细胞分泌模型有机阴离子--二硝基苯基谷胱甘肽(GS-DNP)的影响。先前的实验已经证明，大鼠肝细胞分泌GS-DNP主要是由这种化合物的小管转运系统介导的。胆汁酸(C)、牛磺胆酸(TC)、牛磺酸脱氧胆酸(TUDC)和甘氨酸或牛磺酸石胆酸(GLC或TLC)预先孵育大鼠肝细胞，对GS-DNP的初始外排速率无影响。而GLC(SGLC)和TLC(STLC)的3-硫酸盐对GS-DNP的外流有抑制作用，SGLC的抑制作用在10微米时达到半峰值。胆酸盐和胆石酸的3-O-葡萄糖醛酸苷(GLucLC)对GS-DNP转运的抑制作用更强，10微米GLucLC对GS-DNP转运的抑制作用达%。其他亲胆汁的有机阴离子也抑制GS-DNP的分泌，尽管浓度较高；在100微米时，胆红素二月桂酸酯，一种胆红素二葡萄糖醛酸脂的类似物，抑制转运48%。另一方面，一些亲胆的阳离子和中性化合物对GS-DNP的外流没有影响。并对氧化谷胱甘肽(GSSG)的肝胆分泌功能进行了研究。在正常离体灌流大鼠肝脏中，GSSG在细胞内氧化还原型谷胱甘肽(GSH)时可见广泛的胆汁分泌。分离的正常肝细胞也能分泌GSSG，100微米的SGLC可抑制95%的GSSG分泌。相反，在分离的灌流肝脏和遗传性结合高胆红素血症的tr突变大鼠的分离肝细胞中，胆汁分泌不存在。这些结果表明，GSSG和GS结合物的小管外流可被多种多价有机阴离子抑制，但不能被阳离子、中性化合物和单离子胆汁酸所抑制。这表明多特异性有机阴离子转运体负责这些多价阴离子的转运，这与突变的TR4大鼠所有这些化合物的胆道转运存在缺陷的事实密切一致。
The effect of a spectrum of organic compounds on the secretion of a model organic anion, dinitrophenylglutathione (GS-DNP), by hepatocytes was tested. Previous experiments have demonstrated that the secretion of GS-DNP from isolated rat hepatocytes is predominantly mediated by a canalicular transport system for this compound. Preincubation of isolated rat hepatocytes with the bile acids cholic acid (C), taurocholic acid (TC), tauroursodeoxycholic acid (TUDC) and glyco- or tauro-lithocholic acid (GLC or TLC) had no effect on the initial efflux rate of GS-DNP. In contrast, the 3-sulphates of GLC (SGLC) and TLC (STLC) did inhibit GS-DNP efflux; half-maximal inhibition with SGLC was reached with 10 microM. The 3-O-glucuronides of both cholate and lithocholate (GlucLC) were even more potent inhibitors of transport; 10 microM-GlucLC inhibited GS-DNP transport by 89%. Other cholephilic organic anions also inhibited GS-DNP secretion, albeit at higher concentrations; at 100 microM, bilirubin ditaurate, an analogue of bilirubin diglucuronide, inhibited transport by 48%. On the other hand, a number of cholephilic cationic and neutral compounds had no effect on GS-DNP efflux. The hepatobiliary secretion of oxidized glutathione (GSSG) was also investigated. In normal isolated perfused rat liver, extensive biliary secretion of GSSG was observed upon intracellular oxidation of reduced glutathione (GSH). GSSG was also actively secreted from isolated normal hepatocytes, and this secretion could be inhibited by 95% by incubation of the cells with 100 microM-SGLC. In contrast, biliary secretion was absent in the isolated perfused liver and in isolated hepatocytes from TR- mutant rats with a hereditary conjugated hyperbilirubinaemia. These results show that the canalicular efflux of GSSG and GS conjugates can be inhibited by a wide variety of polyvalent organic anions, but not by cations, neutral compounds and unianionic bile acids. This suggests that a multispecific organic-anion transporter is responsible for transport of these polyvalent anions, which is in close agreement with the fact that the biliary transport of all these compounds is defective in the mutant TR4 rat.