Kv1.4通道电流与大鼠心室肌细胞瞬间外向钾电流特性的比较

克隆的大鼠外向钾通道Ｋｖ１．４亚型表达于２９３细胞（ＲＣＫ４）。用膜片钳全细胞钳制法系统比较该克隆的大鼠瞬间外向钾电流（Ｉｔｏ）和天然大鼠心室肌细胞Ｉｔｏ的特点和动力学特性。两种通道电流形态相似,呈“Ａ”型电流,在＋４０ｍＶ时电流失活时间常数τ依次为３６．６±２ｍｓ和４１．０±２ｍｓ（Ｐ＞０．０５）。Ｋｖ１．４通道电流激活曲线用二相Ｂｏｌｔｚｍａｎｎ方程拟合,一相半数最大激活电位（Ｖ１／２,１）为－２１．０±３．９ｍＶ、二相半数最大激活电位（Ｖ１／２,２）为２７．０±３．９ｍＶ;天然大鼠心室肌细胞Ｉｔｏ激活曲线用单相Ｂｏｌｔｚｍａｎｎ方程拟合,半数最大激活电位为１０．８±１．１ｍＶ（Ｐ＜０．０５,ｖｓＫｖ１．４通道电流的Ｖ１／２,１）。ＲＣＫ４细胞通道电流半数最大灭活电位（Ｖ１／２）为－４９．８±１．８ｍＶ,斜率因子（ｋ）为３．８±０．２７;天然大鼠心室肌细胞Ｉｔｏ的Ｖ１／２为－３１．６±１．７ｍＶ,ｋ为５．４±０．２１。灭活后再激活的恢复时间比较,Ｋｖ１．４通道电流明显长于天然大鼠心室肌细胞Ｉｔｏ,分别为１．８９±０．２ｓ和３９．２±１．６ｍｓ（Ｐ＜０．０５）。研究表明克隆的大鼠Ｋｖ１．４通道电流与天然大?

Comparing Electrophysiological Properties of Kv1.4 Potassium Channel Current With Native Transient Outward Potassium Current in Rat Ventricular Myocytes

Cloned rat potassium channels,RCK4 (subtype Kv1.4) were stably expressed in 293 cells. The electrophysiological properties of RCK4 were compared with rat heart transient outward potassium currents (Ito) by using the patch clamp whole cell recording techniques.Both currents showed "A" type current properties with an inactivation time constant(τ) of 36.6±2 ms(Kv 1.4) and 41±2 ms(rat heart Ito,P>0.05) at +40mV,respectively.The activation curve of Kv1.4 current was better fitted by double sigmodal function with first half maximal activation voltage (V1/2,1) of -21.0±3.9 mV,and second half maximal voltage(V1/2,2) of 27.0±3.9 mV.While the activation curve of Ito current in rat ventricular myocytes was better fitted by simple Boltzmann function with V1/2 of 10.8±1.1 mV(P<0.05,vs V1/2,1).The steady state inactivation curves showed that the voltage for half maximal inactivation was -49.8±1.8 mV in RCK4 cells and -31.6±1.7 mV in rat myocytes, and the slope factor(k) were 3.8±0.27 and 5.4±0.21,respectively.Comparison of the rate of recovery from inactivation of two potassium channels,the recovery rate of Kv1.4 currents were significant slower than that of rat heart Ito.The time constants(τ) were 1.89±0.2 s and 39.2±1.6 ms(P<0.05) in Kv1.4 and in rat heart Ito, respectively.Our study shows that the currents of Kv1.4 are quite different from native cardiac Ito in electrophysiological properties and demonstrated that channels for rat heart Ito might not be composed by Kv1.4 homologously.