Di Monte D, Ross D, Bellomo G, Eklöw L, Orrenius S
Arch Biochem Biophys. 1984 Dec;235(2):334-42. doi: 10.1016/0003-9861(84)90206-6.
The effects of menadione (2-methyl-1,4-naphthoquinone) metabolism on intracellular soluble and protein-bound thiols were investigated in freshly isolated rat hepatocytes. Menadione was found to cause a dose-dependent decrease in intracellular glutathione (GSH) level by three different mechanisms: (a) Oxidation of GSH to glutathione disulfide (GSSG) accounted for 75% of the total GSH loss; (b) About 15% of the cellular GSH reacted directly with menadione to produce a GSH-menadione conjugate which, once formed, was excreted by the cells into the medium; (c) A small amount of GSH (approximately 10%) was recovered by reductive treatment of cell protein with NaBH4, indicating that GSH-protein mixed disulfides were also formed as a result of menadione metabolism. Incubation of hepatocytes with high concentrations of menadione (greater than 200 microM) also induced a marked decrease in protein sulfhydryl groups; this was due to arylation as well as oxidation. Binding of menadione represented, however, a relatively small fraction of the total loss of cellular sulfhydryl groups, since it was possible to recover about 80% of the protein thiols by reductive treatments which did not affect protein binding. This suggests that the loss of protein sulfhydryl groups, like that of GSH, was mainly a result of oxidative processes occurring within the cell during the metabolism of menadione.
在新鲜分离的大鼠肝细胞中研究了甲萘醌（2-甲基-1,4-萘醌）代谢对细胞内可溶性和蛋白质结合硫醇的影响。发现甲萘醌通过三种不同机制导致细胞内谷胱甘肽（GSH）水平呈剂量依赖性降低：（a）GSH氧化为谷胱甘肽二硫化物（GSSG）占总GSH损失的75%；（b）约15%的细胞内GSH直接与甲萘醌反应生成GSH-甲萘醌缀合物，一旦形成，该缀合物就会被细胞排泄到培养基中；（c）用NaBH4对细胞蛋白质进行还原处理可回收少量GSH（约10%），这表明GSH-蛋白质混合二硫化物也是甲萘醌代谢的结果。用高浓度甲萘醌（大于200 microM）孵育肝细胞也会导致蛋白质巯基显著减少；这是由于芳基化以及氧化作用。然而，甲萘醌的结合仅占细胞巯基总损失的相对较小部分，因为通过不影响蛋白质结合的还原处理可以回收约80%的蛋白质硫醇。这表明蛋白质巯基的损失与GSH的损失一样，主要是甲萘醌代谢过程中细胞内发生的氧化过程的结果。
