The mechanism of biliary secretion of reduced glutathione. Analysis of transport process in isolated rat-liver canalicular membrane vesicles.
The mechanism of biliary secretion of reduced glutathione. Analysis of transport process in isolated rat-liver canalicular membrane vesicles.
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胆汁分泌还原型谷胱甘肽的机制。
DOI：
10.1111/j.1432-1033.1983.tb07590.x
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Arias,IM
中科院分区：
文献类型：
--
作者：
Inoue,M;Kinne,R;Tran,T;Arias,IM
用快速过滤法研究了还原型谷胱甘肽（GSH）在离体大鼠肝小管膜泡中的转运。膜囊泡显示[2 - 3 H]甘氨酸标记的GSH被摄取到具有免疫反应性的囊泡内空间。尽管小管膜囊泡具有γ-谷氨酰转移酶和氨肽酶M，将谷胱甘肽水解为组分氨基酸的酶，但通过L-（αS，5，S）-α-氨基-3-氯-4，5-二氢-5-异恶唑乙酸（AT-125）亲和标记灭活囊泡相关转移酶对GSH转运的初始速率没有影响。化学分析显示，完整的GSH占囊泡相关放射性的大部分。运输的初始速率遵循相对于GSH浓度的饱和动力学;计算出20 s内的表观Km为0.33 mM，V为1.47 nmol/mg蛋白。这些结果表明，GSH跨小管膜转运是一个载体介导的过程。NaCl在运输介质中的KCl，氯化锂或氯化胆碱的更换没有影响的小泡的运输活动。缬氨霉素诱导的K+扩散电位（囊泡内部为正）可提高囊泡的GSH摄取速率，丙磺舒可抑制该速率，表明GSH通过小管膜的转运是产电的，涉及负电荷的转移。GSH的转运被氧化型谷胱甘肽或S-苄基-谷胱甘肽抑制。小管质膜中的这种转运系统可能在GSH及其衍生物的胆汁分泌中起作用，GSH及其衍生物通过氧化过程或谷胱甘肽S-转移酶在肝细胞中合成。
Transport of reduced glutathione (GSH) was studied in isolated rat liver canalicular membrane vesicles by a rapid filtration technique. The membrane vesicles exhibit uptake of [2‐3H]glycine–labeled GSH into an osmotically reactive intravesicular space. Althought the canalicular membrane vesicles possess γ‐glutamyltransferase and aminopeptidase M, enzymes that hydrolyze glutathione into component amino acids, inactivation of the vesicle associated transferase by affinity labeling with L‐(αS,5,S)‐α‐amino‐3‐chloro‐4,5‐dihydro‐5‐isoxazoleacetic acid (AT‐125) had no effect on the initial rate of GSH transport. Chemical analysis revealed that intact GSH accounted for most of vesicle‐associated radioactivity. The initial rate of transport followed saturation kinetics with respect to GSH concentration; an apparentKmof 0.33 mM andVof 1.47 nmol/mg protein in 20 s were calculated. These results indicate that transport of GSH across the canalicular membranes is a carrier‐mediated process. Replacement of NaCl in the transport medium by KCl, LiCl or choline chloride had no effect on the transport activity of the vesicles. The rate of GSH uptake by the vesicles was enhanced by valinomycin‐induced K+‐diffusion potential (vesicle inside positive) and was inhibited by probenecid, indicating that GSH transport across the canalicular membranes is electrogenic and involves the transfer of negative charge. The transport of GSH was inhibited by oxidized glutathione orS‐benzyl‐glutathione. This transport system in canalicular plasma membranes may function in biliary secretion of GSH and its derivatives which are synthesized in hepatocytes by oxidative processes or glutathioneS‐transferase.