Gintant G A, Datyner N B, Cohen I S
Biophys J. 1985 Dec;48(6):1059-64. doi: 10.1016/S0006-3495(85)83869-8.
Studies of time-dependent, plateau outward current (delayed rectification) in the heart are complicated by the accumulation and depletion of K+ ions in intercellular clefts. To minimize this problem, we studied delayed rectification in acutely isolated (enzymic solution, gentle agitation) canine cardiac Purkinje myocytes using the single microelectrode voltage-clamp technique. We found a sigmoidal voltage-dependence for activation of outward plateau current, with maximal activation occurring at potentials near -10 mV. The activation and deactivation of plateau outward current was adequately described as the sum of a fast and slow exponential component. A comparison of the time course of activation of plateau outward current and the "envelope" of tail currents suggests that a single voltage-gated conductance with one open and two closed states can account for delayed rectification in Purkinje myocytes. These results differ from those previously obtained with intact sheep Purkinje fibers in which two time-dependent conductances were postulated to account for delayed rectification (Noble, D., and R. W. Tsien, 1969, J. Physiol. (Lond.), 200:205-231).
心脏中随时间变化的平台外向电流（延迟整流）的研究因细胞间缝隙中钾离子的积累和消耗而变得复杂。为了尽量减少这个问题，我们使用单微电极电压钳技术，对急性分离（酶溶液，轻柔搅拌）的犬心脏浦肯野心肌细胞中的延迟整流进行了研究。我们发现外向平台电流激活具有S形电压依赖性，最大激活发生在接近-10 mV的电位。平台外向电流的激活和失活被充分描述为快速和慢速指数成分的总和。平台外向电流激活的时间进程与尾电流“包络”的比较表明，具有一个开放状态和两个关闭状态的单一电压门控电导可以解释浦肯野心肌细胞中的延迟整流。这些结果与先前在完整绵羊浦肯野纤维中获得的结果不同，在完整绵羊浦肯野纤维中，假设两种随时间变化的电导来解释延迟整流（诺布尔，D.，和R.W.钱恩，1969年，《生理学杂志》（伦敦），200:205-231）。
