Ballatori N, Truong A T, Ma A K, Boyer J L
Department of Biophysics, Environmental Health Sciences Center, University of Rochester School of Medicine, New York 14642.
Am J Physiol. 1989 Mar;256(3 Pt 1):G482-90. doi: 10.1152/ajpgi.1989.256.3.G482.
Utilizing the isolated perfused rat liver, we examined several factors influencing efflux of glutathione [reduced glutathione (GSH) and glutathione disulfide (GSSG)] into perfusate and bile, including the effects of perfusate composition, oxygen delivery to the liver, and acivicin (AT-125), an inhibitor of gamma-glutamyl transferase activity. When livers were perfused with a recirculating Krebs-Ringer bicarbonate buffer only 7-26% of released glutathione was excreted into bile, mainly in its oxidized form (71-90% as GSSG). In contrast, when 20% bovine red blood cells or 20% fluorocarbon emulsion were utilized as perfusates, biliary glutathione accounted for a larger fraction of total hepatic efflux (16-41%), and only 39-65% was excreted as GSSG. To determine whether O2 delivery to the liver could explain some of these differences, biliary and sinusoidal efflux of glutathione were measured as O2 delivery was varied by 1) increasing the perfusion flow rate, 2) altering the concentration of fluorocarbon emulsion (5, 10, and 20%), and 3) changing the PO2 (95% O2-5% CO2 vs. 50% O2-5% CO2-45% N2). Under all experimental conditions, an increase in O2 delivery was accompanied by an increase in bile flow and in the concentration and rate of glutathione efflux into bile but no significant change in sinusoidal efflux of glutathione. Hepatic tissue GSH and GSSG levels were not affected by the various treatments. When gamma-glutamyl transferase activity was inhibited with AT-125, biliary glutathione increased to levels of approximately 50% of total hepatic efflux in fluorocarbon-perfused livers, and only 24-29% of the glutathione was excreted as GSSG.(ABSTRACT TRUNCATED AT 250 WORDS)
利用离体灌注大鼠肝脏，我们研究了影响谷胱甘肽（还原型谷胱甘肽（GSH）和氧化型谷胱甘肽（GSSG））向灌注液和胆汁中流出的几个因素，包括灌注液成分、肝脏的氧气供应以及γ-谷氨酰转移酶活性抑制剂阿西维辛（AT-125）的影响。当肝脏仅用循环的 Krebs-Ringer 碳酸氢盐缓冲液灌注时，释放的谷胱甘肽中只有 7-26%以氧化形式（71-90%为 GSSG）排泄到胆汁中。相比之下，当使用 20%的牛红细胞或 20%的氟碳乳剂作为灌注液时，胆汁中的谷胱甘肽占肝脏总流出量的比例更大（16-41%），并且只有 39-65%以 GSSG 的形式排泄。为了确定肝脏的氧气供应是否可以解释其中一些差异，通过以下方式改变氧气供应来测量谷胱甘肽的胆汁和窦状隙流出量：1）增加灌注流速，2）改变氟碳乳剂的浓度（5%、10%和 20%），3）改变 PO2（95% O2-5% CO2 与 50% O2-5% CO2-45% N2）。在所有实验条件下，氧气供应增加伴随着胆汁流量以及谷胱甘肽向胆汁中的浓度和流出速率增加，但谷胱甘肽的窦状隙流出量没有显著变化。肝脏组织中的 GSH 和 GSSG 水平不受各种处理的影响。当用 AT-125 抑制γ-谷氨酰转移酶活性时，在氟碳灌注的肝脏中，胆汁中的谷胱甘肽增加到肝脏总流出量的约 50%，并且只有 24-29%的谷胱甘肽以 GSSG 的形式排泄。（摘要截断于 250 字）
