γ-谷氨酰转肽酶在心肌梗死大鼠心肌Ito通道重构机制中的作用

Effect of γ-glutamyl transpeptidase on Ito channel remodeling in rat heart post-myocardial infarction

目的:研究心肌梗死(心梗)后心肌钾通道重构是否与γ-谷氨酰转肽酶(GGT)活性调控相关联。方法:取体重180～200g的雄性SD大鼠,建立心梗动物模型(心梗组);另取大鼠(对照组)进行同样手术,但不结扎冠状动脉。两组大鼠术后6～8周提取心肌细胞膜蛋白,用生物化学法分析GGT活性,用Real-Time PCR分析GGT的mRNA表达,用Western blotting分析GGT蛋白表达。酶解法获得单一心室肌细胞,应用全细胞膜片钳技术记录瞬时外向钾电流(Ito)。结果:①心梗组心肌GGT活性较对照组显著增加(左心室增加45%,室间隔增加31%),GGT的mRNA和蛋白表达亦显著增加;②心梗组左室肌细胞Ito密度较对照组显著降低[(16.2±3.1)pA/pF∶(30.9±3.8)pA/pF,P<0.05];经细胞外还原型谷胱甘肽(GSHo)预处理4～5h后,心梗组Ito密度恢复至对照组水平[(30.1±3.3)pA/pF∶(30.9±3.8)pA/pF,P>0.05];③GSHo完全抑制了GGT特异性阻滞剂对Ito密度的正常化,但不影响N-乙酰半胱氨酸对Ito密度的正常化。结论:GGT介导了细胞外GSHo对Ito通道的脱重构作用,调控钾通道的功能表达;GGT对GSHo的催化分解可逆转心肌电重构。

Objective：To identify whether GGT activity is relative to Kv channel remodeling in post-myocardial infarction. Method：We selected 180-200 g male SD rats to establish myocardial infarction （MI） model （MI group）, and control group that have the same operation with the MI group but without ligation of coronary artery. 6- 8 weeks after operation, we extracted cell membrane proteins of myocardium, then analyzed GGT activity with biological chemical method, dected GGT mRNA expression with Real Time PCR, and tested GGT protein expression with Western blotting. Single ventricular myocytes were obtained by enzymatic method, and Ito was recorded by whole cell patch damp technique. Result：（1）Compared with control group, GGT activity in MI group increased significantly （left ventricular increased 45 %, ventricular septal increased 31 %）, while expressions of GGT mRNA and protein increased significantly too. （DThe density of Ito decreased significantly in MI group than that in control group [（16.2±3.1）pA/pF vs （30.9±3.8）pA/pF, P〈0.05], then was recovery to the level of control group after preconditioning with GSHo in 4-5 h [（30.14±3.3）pA/pF vs （30.9±3.8）pA/pF, P〉0.05]. （3）The functions of GGT specific blockers on Ito density were completely inhibited by GSHo, but the effect of NAC on Ito density didn＇t affected by GSHo. Conclusion： GGT mediates the remodling effect of GSHo on ho channels. The catalytic decomposition of GGT could be used as a clinical treatment strategy to reverse cardiac electrical remodeling.