Up-regulation of K(+) channels in diabetic rat ventricular myocytes by insulin and glutathione.
Up-regulation of K(+) channels in diabetic rat ventricular myocytes by insulin and glutathione.
复制标题
胰岛素和谷胱甘肽上调糖尿病大鼠心室肌细胞中 K( ) 通道。
DOI：
10.1016/s0008-6363(01)00446-1
复制
发表时间：
2002
影响因子：
10.8
通讯作者：
Rozanski,GeorgeJ
中科院分区：
文献类型：
--
作者：
Xu,Zhi;Patel,KaushikP;Lou,MarjorieF;Rozanski,GeorgeJ
目的：糖尿病的心脏发病机制与氧化应激有关，氧化应激引起细胞功能的内源性调节因子--心肌谷胱甘肽发生深刻变化。本研究探讨了谷胱甘肽对糖尿病大鼠心室肌细胞K+通道活性的调节作用及其与胰岛素信号的关系。方法和结果：比色分析显示，实验性糖尿病大鼠心肌组织中还原型谷胱甘肽(GSH)的基础水平明显低于假手术对照组，这与氧化应激条件一致。这种谷胱甘肽状态的改变与γ-谷氨酰半胱氨酸合成酶活性的显著降低相平行，GSH-谷氨酰半胱氨酸合成酶是参与谷胱甘肽稳态的主要途径。电压钳研究证实，与对照组相比，携带瞬时外向电流(Ito)的K+通道在糖尿病状态下下调，这种电生理变化可被胰岛素体外处理2-3h逆转。与未处理的心肌细胞相比，GSH孵育糖尿病大鼠心肌细胞也使Ito密度正常化，但时间比胰岛素长。用谷胱甘肽还原酶抑制剂1，3-二氯乙基亚硝脲或γ-谷氨酰半胱氨酸合成酶阻断剂丁硫氨酸亚磺胺检测糖尿病大鼠心肌细胞的胰岛素反应性，以确定Itoby胰岛素上调是否是通过改变心肌细胞谷胱甘肽。结论：氧化应激诱导的GSH氧化还原状态的改变在调节Ito通道功能中起重要作用，心肌细胞GSH的稳态与胰岛素信号转导有关。
Objective:The cardiac pathogenesis of diabetes mellitus involves oxidative stress that elicits profound changes in myocardial glutathione, an endogenous regulator of cell function. This study examined the role of glutathione in regulating K+channel activity in isolated ventricular myocytes from diabetic rats and its relationship to insulin signaling.Methods and results:Colorimetric analysis of extracts of ventricular tissue from Sprague–Dawley rats showed that the basal level of reduced glutathione (GSH) was significantly less in rats with experimental diabetes compared with sham controls, consistent with oxidative stress conditions. This change in GSH status paralleled a significant decrease in the activity of γ-glutamylcysteine synthetase, a major pathway involved in GSH homeostasis. Voltage-clamp studies confirmed that, compared with control myocytes, K+channels carrying the transient outward current (Ito) are down-regulated in the diabetic state and that this electrophysiological change is reversed by in vitro treatment with insulin for 2–3 h. Incubation of diabetic rat myocytes with GSH also normalized Itodensity compared with untreated myocytes, but with a longer time course than insulin. To determine if up-regulation of Itoby insulin was mediated by alterations in myocyte GSH, insulin-responsiveness of diabetic rat myocytes was tested in the presence of 1,3-bis-chloroethyl-nitrosourea, an inhibitor of glutathione reductase, or buthionine sulfoximine, a blocker of γ-glutamylcysteine synthetase. Neither blocker alone altered Itodensity in diabetic rat myocytes when compared with untreated cells, but each blocked the effect of insulin to up-regulate Ito.Conclusions:These data suggest that oxidative stress-induced alteration in GSH redox state plays an important role in regulating Itochannel function and that GSH homeostasis in ventricular myocytes is functionally coupled to insulin signaling.