目的　探讨犬右心室心外膜下 (Epi)细胞复极 1期瞬间外向钾电流 (Ito1)的电生理特性。方法　应用全细胞钳制技术 ,对右心室Epi细胞复极 1期Ito1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Epi细胞具有强大的Ito1,其激活过程呈明显的电压依赖性 ,在37℃、0 2Hz和去极化试验电压为 +70mV时 ,Epi细胞的峰值Ito1强度和密度分别达 (4 15 0± 1780 )pA和 (31± 11 4)pA/pF ,其激活和失活动力学过程符合Boltzmann分布 ;(2 )犬右心室Epi细胞Ito1具有明显的频率依赖性 ,即在基础刺激周长增加时 ,Ito1明显增大 ,并和动作电位的“尖峰 穹隆”幅度的增加相对应 ;(3)温度对Ito1强度的影响明显 ,在去极化试验电压为 +70mV、0 2Hz和温度为 2 2℃、37℃条件下 ,右心室Epi细胞的Ito1强度和密度分别为 (2 380± 10 5 0 )pA与 (18± 7 6 )pA/pF、(4 15 0± 1780 )pA与 (31± 11 4)pA/pF ,差异明显。结论　犬右心室Epi细胞存在强大的Ito1,这种具有明显电压依赖性、频率依赖性和温度依赖性的Ito1及其参与介导的“尖峰 穹隆”状动作电位图形是右心室Epi细胞复极1期一个突出的电生理特点。 Objective To investigate the electrophysiological characteristics of transient outward potassium current (Ito1) in repolarization phase 1 of canine right ventricular epicardial (Epi) cells. Methods Whole cell clamp technique was used to quantitatively observe the current intensity, kinetic process and action potential notch of Ito1 in repolarized Epi cells of right ventricle. Results (1) Epi cells in canine right ventricle had strong Ito1, and the activation process was obviously voltage-dependent. The peak Ito1 intensity and density of Epi cells at 37 ℃, 0 2Hz and the depolarization test voltage was + 70mV respectively (4 15 0 ± 1780) pA and (31 ± 11 4) pA / pF, respectively. The activation and inactivation kinetics were in accordance with Boltzmann distribution. (2) Ito1 in canine right ventricular Epi cells had obvious frequency dependence, Ito1 increased significantly with the increase of perimeter, and corresponded with the increase of the amplitude of “peak dome” of action potential. (3) The effect of temperature on Ito1 intensity was obvious. When the depolarization test voltage was + 70mV, 0 2Hz and The Ito1 intensity and density of Epi cells in right ventricle were (2 380 ± 10 5 0) pA and (18 ± 7 6) pA / pF, (4 15 0 ± 1780) pA And (31 ± 11 4) pA / pF, the difference is obvious. Conclusions The presence of a strong Ito1 in Epi cells of canine right ventricle, which is obviously voltage-dependent, frequency-dependent and temperature-dependent, and its participation in “peak vault” -like action potential pattern is induced by repolarization of right ventricle Epi cells 1 A prominent electrophysiological characteristics.