模拟缺血对三层心室肌细胞快钠通道I-V曲线的影响及临床意义

目的探讨心肌缺血时折返性心律失常发生的离子机制。方法以酶解法分离兔心室肌三层细胞 ,先后用正常和缺血灌流模拟正常和缺血状态 ,并采用膜片钳全细胞记录法观察缺血对三层心室肌细胞快钠通道I V曲线的影响。结果缺血后三层细胞的钠电流 (INa)电压依赖性、I V曲线的形态轨迹未变 ,INa峰电流密度减小 ,三层细胞间峰电流密度差异发生变化。结论心肌缺血影响三层细胞间INa的异质性及三层细胞离子通道电流平衡 ,构成心律失常发生的基质 ,并可部分解释三层细胞在正常和缺血状态对药物的不同反应。

EFFECT OF SIMULATED ISCHEMIA ON I-V CURVES OF Na+ CHANNEL IN RABBIT VENTRICULAR EPICARDIAL,MIDMYOCARDIAL AND ENDOCARDIA MYOCYTES

ObjectiveTo study the ionic mechanism of reentrant arrhythmia in myocarolial ischemia. MethodsSingle myocytes were enzymatically isolated from the epicardium, midmyocardium and endocardium of the free left ventricle wall of rabbit, then I Na of the three cellular subtypes (superfused with normal and then simulated ischemia solution) were recorded using whole-cell patch-clamp techniques. The currents were compared in the three cellular subtypes before and after 10, 20, 30 min simulated ischemia. ResultsThere were no changes in the configuration of I Na I-V curves and the dependence of voltage after simulated ischemia. The peak I Na densities (at -20 mV) were significantly reduced in three cellular subtypes compared those before simulated ischemia with those in normal condition. Meanwhile, the differences of I Na peak current densities in three cellular subtypes were changed after simulated ischemia. ConclusionIschemia can affect the balance of ion channel currents in three cellular subtypes and the heterogeneity of I Na among three celluar subtypes. These are responsible for arrhythmias and can be reasons of different pharmacology reactions under normal and ischemia in three cellular subtypes in some degree.