瞬时外向钾电流在糖尿病心肌病电重构中的作用

目的：探讨糖尿病心肌病（DCM）大鼠心室肌细胞瞬时外向钾电流（Ito）的变化，了解其在电重构中的作用。方法选用20只健康成年SD大鼠，随机分为对照组（n=10）和DCM组（n=10），并通过病理组织学证实为DCM心肌病理学改变。分别对两组大鼠采用改进的耐钙成年大鼠急性酶分离方法分离心肌细胞，运用膜片钳技术以全细胞模式分别记录两组大鼠心室肌单细胞的Ito和膜电容，并分析比较两组大鼠心室肌Ito的变化。结果与对照组比较，DCM组大鼠左心室心肌细胞的Ito电流密度显著低于对照组＋70 mV时，（16.80±9.10） pA/pF v s（36.25±5.20）pA/pF]（P〈0.05），DCM组的Ito的I-V曲线明显较对照组下移。结论 DCM的Ito数量明显减少，在DCM心肌电重构中起着重要作用。 Ito的减少及Ito通道的分布密度不同，可导致动作电位时程与有效不应期发生变化，可能与临床严重心律失常的发生有关。

Effect of transient outward potassium current on ventricular electrophysi-ological remodeling in diabetic cardiomyopathy

Objective To investigate the changes of the transient outward potassium current （Ito） on ventricular my-ocardium in diabetic cardiomyopathy （DCM） rat and to explore the meaning of theses changes for ventricular electro-physiological remodeling. Methods 20 healthy adult Spprague-dawley rats were selected and randomly divided into control group （n=10） and DCM group （n=10）.The myocardial pathological alterations of DCM were identified in DCM group by histopathologic test,and cardiomyocytes in both groups were separated by advanced calcium-tolerant separa-tion method.Whole-cell path clamp technique was used to record the unicellular changes of Ito and membrane capaci-tance in left ventricular myocytes for DCM and control group respectively.All data were analysed and compaired by software. Results Compared with control group,the Ito density on left ventricular myocytes was significantly lower in DCM group than that of the control group （16.80±9.10） pA/pF vs （36.25±5.20） pA/pF,at ＋70 mV]（P〈0.05）,and the I-V curve of Ito in DCM group was more depressed than the control group markedly. Conclusion The changes of Ito play an important role in cardiac electrophysiological remodeling of diabetic cardiomyopathy.The reduction of Ito and the variations of Ito density may be lead to the modifications of action potential duration and effective refractory period, which associates with severe arrthymia.