Li C, Zeng Y M, Zhuang C X, Liu T F
Department of Physiology, Shantou University Medical College, PR China.
Methods Find Exp Clin Pharmacol. 1992 Mar;14(2):107-13.
1.5 mM KCl Tyrode's solution enabled the critical potential (-55-60 mV) of effective refractory period to shift in a positive direction in guinea pig ventricular muscle cells. In 1.5 mM KCl Tyrode's solution, the probability of testing AP's initial potential positive to -54 mV in the repolarizing phase was as high as 80% (n = 10), but the percentage in 4.5 mM [K]o group was only 11% (n = 35). The mean value of the positive shift was 30.2 +/- SD 17 mV. Testing APs had higher values of overshoots (mean = 23 +/- 13.8 mV); their mean Vmax was 98 V/s. Early after depolarization and positive inotropic effects appeared. 13.5 mM KCl, in contrast to 1.5 mM KCl, produced contrary effects. Phenomena indicated that early after depolarization in low [K]o was associated with the positive shift of critical potential of effective refractory period. Above-mentioned effects of 1.5 mM KCl could not be completely eliminated by verapamil, but could be abolished by an inactivation promoting agent of sodium channel, lidocaine 7.4 x 10(-5) M (n = 10). The results suggest that accelerating recovery time and shifting recovery potential in the positive direction of inactivated sodium channel might be the principal reasons for the effects of low [K]o. The role of the Na+ pump inhibitor, ouabain, was not similar to that of 1.5 mM KCl Tyrode's solution except for positive inotropic effect.
1.5 mM氯化钾的台氏液可使豚鼠心室肌细胞有效不应期的临界电位（-55 - 60 mV）正向偏移。在1.5 mM氯化钾的台氏液中，复极化阶段动作电位（AP）初始电位正向超过 -54 mV的检测概率高达80%（n = 10），但在4.5 mM [K]o组中该百分比仅为11%（n = 35）。正向偏移的平均值为30.2 +/-标准差17 mV。检测到的动作电位有更高的超射值（平均值 = 23 +/- 13.8 mV）；其平均最大上升速率为98 V/s。出现了早期后去极化和正性肌力作用。与1.5 mM氯化钾相比，13.5 mM氯化钾产生相反的作用。这些现象表明低[K]o时的早期后去极化与有效不应期临界电位的正向偏移有关。1.5 mM氯化钾的上述作用不能被维拉帕米完全消除，但可被钠通道失活促进剂7.4 x 10(-5) M的利多卡因消除（n = 10）。结果表明，加速失活钠通道的恢复时间并使其恢复电位正向偏移可能是低[K]o产生这些作用的主要原因。除正性肌力作用外，钠泵抑制剂哇巴因的作用与1.5 mM氯化钾台氏液的作用不同。
