犬右心室M细胞复极1期瞬间外向钾电流特性的研究

目的:探讨犬右心室M细胞复极1期瞬间外向钾电流(Ito₁)的电生理特性。方法:应用膜片钳技术,对犬右心室M细胞复极1期Ito₁离子流的电流强度、动力学过程和动作电位切迹进行定量观察。结果:(1)犬右心室M细胞Ito₁离子流的激活过程呈明显的电压依赖性,在37℃、刺激周长为5000ms、去极化电压为0mV和+70mV时,其峰值Ito₁离子流的强度和密度分别为(690±380)pA和(3130±1910)pA,差异显著(P＜0.01);(2)犬右心室M细胞Ito₁离子流具有明显的频率依赖性,在37℃、去极化试验电压为+70mV和基础刺激周长为500ms及5000ms时,Ito₁离子流的强度分别为(1690±830)pA和(3130±1910)pA,差异显著(P＜0.01),并与动作电位的"尖峰-和穹隆"幅度的增加相对应。结论:强大的Ito₁离子流及其介导的"尖峰-和穹隆"状动作电位图形是犬右心室M细胞一个突出的电生理特点之一。

Characteristics of transient outward potassium current in repolarization 1 phase from the canine right ventricular mid-myocardial cells

AIM: To examine the electrophysiological characteristics of transient outward potassium current(Ito₁) in repolarization 1 phase from the canine right ventricular M cells. METHODS: By use of whole cell patch-clamp technique, we quantitatively researched the ionic intensity, density of Ito₁ and the notch magnitude of action potential in repolarization 1 phase. RESULTS: (1) The activating process of Ito₁ of canine right ventricular M cells presented evident voltage-dependency. Under the condition of 37℃, 5 000 ms, 0 mV and +70 mV, the average peak Ito₁ intensity of right ventricular M cell were (690±380) pA and (3 130±1 910) pA, respectively (P＜0.01). (2) The Ito₁ intensity of canine right ventricular M cell possessed obvious frequent dependency. Under the condition of 37℃,+70 mV, 500 ms and 5 000 ms, the average peak Ito₁ intensity were (1 690±830) pA,(3 130±1 910) pA, respectively(P＜0.01), corresponding to the increase of action potential "spike-dome" magnitude in repolarization 1 phase. CONCLUSION: Potent Ito₁ as well as the "spike-dome"-like action potential figure mediated by Ito₁ is one of the prominent electrophysiological characteristics of the canine right ventricular M cells.