对乙酰氨基酚致小鼠肝微粒体谷胱甘肽S-转移酶的激活机制

目的　探索大剂量对乙酰氨基酚 (Par)在体内对小鼠肝微粒体谷胱甘肽S 转移酶(mGST)活性的影响及其可能的机制。方法　小鼠饮用 1 0 %乙醇 7d以诱导肝药酶 ,Par90 ,1 5 0 ,2 1 0mg·kg-1ip ,在 6h内测定肝mGST活性及谷胱甘肽 (GSH)含量 ,结合二硫苏糖醇(DTT)逆转与N 乙基马来酰亚胺 (NEM)激活效应来探讨mGST活性变化机制 ,并用SDS PAGE和负染凝胶法评价Par对mGST蛋白分子量及含量的影响。结果　ipPar90～ 2 1 0mg·kg-1,在短时间内引起小鼠mGST活性增加 ,GSH含量减少。mGST活性的改变与Par处理之间存在时效及量效关系。Par引起的mGST的激活效应不被二硫键断裂剂DTT逆转 ,NEM在Par激活的mGST半胱氨酸 49巯基 (Cys 49 SH)上总激活效应降低 ;激活的mGST未见蛋白分子量变迁及蛋白表达增加。结论　大剂量Par引起小鼠体内mGST活性增加 ,其激活机制主要与Cys 49 SH上单个巯基的修饰激活有关

Mechanism of activation of mouse liver microsomal glutathion S-transferase enhanced by paracetamol treatment in vivo

AIM To explore the influence of over dosage paracetamol(Par) on liver microsomal glutathion S-transferase(mGST) activity of mice and the possible mechanism in vivo. METHODS Mice drank 10% ethanol as CYP inducer for 7 d followed by ip Par 90, 150, 210 mg·kg^-1. The mGST activity and glutathion(GSH) content were measured at different time within 6 h, the mechanism of mGST activation was confirmed by both reversed effects of dithiothreitol(DTT) and reactivated effects of N-ethylmaleimide on mGST. The changes in molecular weight and protein expression were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and negative dye gel. RESULTS mGST activity was increased, and GSH content was decreased compared with those in control by Par(90－210 mg·kg^-1) in short time (P<0.05, P<0.01). The mGST activity was dose and time- dependent on Par treatment. The activity was not conversed by DTT, and mGST total activation on Cys-49-SH by alkylating agent N-ethylmaleimide was decreased. Both enzyme molecular weight and protein express of activated mGST by Par had no obvious changes. CONCLUSION The mGST activition by over- dosage of Par is mainly due to the unique sulfhydryl modification on Cys-49-SH.