Hotokebuchi N, Yano T, Nishizono Y, Nishi K
Department of Pharmacology, Kumamoto University Medical School, Japan.
Jpn J Physiol. 1987;37(5):797-819. doi: 10.2170/jjphysiol.37.797.
We measured changes in membrane potential (MP), extra- and intracellular potassium and intracellular sodium ion activities (aKo, aKi, and aNai) in papillary muscle of the guinea-pig heart induced by repetitive stimulation at various frequencies and periods in vitro, using double-barrelled ion-selective microelectrodes. Stimulation (2-4 Hz) depolarized the cells, and termination of stimulation induced hyperpolarization. The aKi and aNai (stimulated at 0.2 Hz) were 92.3 +/- 4.6 and 7.8 +/- 2.0 mM (mean +/- S.D.), respectively. Prolongation of the stimulation period (0.5-2 min) increased aNai time-dependently, but there was no further increase by stimulation for longer than 3 min. The increase in aNai was dependent on stimulus frequency. After termination of the stimulation aiNa declined exponentially. aKi slightly decreased by the stimulation (3-4 Hz). aKo increased during the stimulation period, and decreased below the initial level after termination of the stimulation. Results suggest that in guinea-pig papillary muscle, the contribution of an electrogenic component of Na-K pump to the hyperpolarization after stimulation would be small, since the hyperpolarization could be explained mostly by depletion of aKo induced by Na-K pump activity.
我们使用双管离子选择性微电极，在体外对豚鼠心脏乳头肌施加不同频率和时长的重复刺激，测量其膜电位（MP）、细胞外和细胞内钾离子以及细胞内钠离子活性（aKo、aKi和aNai）的变化。刺激（2 - 4Hz）使细胞去极化，刺激终止则诱导超极化。在0.2Hz刺激下，aKi和aNai分别为92.3±4.6和7.8±2.0mM（平均值±标准差）。刺激时长延长（0.5 - 2分钟）会使aNai随时间依赖性增加，但刺激超过3分钟后不再进一步增加。aNai的增加取决于刺激频率。刺激终止后，aiNa呈指数下降。aKi在3 - 4Hz刺激下略有下降。aKo在刺激期间增加，刺激终止后降至初始水平以下。结果表明，在豚鼠乳头肌中，钠钾泵的电生成分对刺激后超极化的贡献可能较小，因为超极化主要可以由钠钾泵活动诱导的aKo耗竭来解释。
