Photoelectric Demonstration of Ouabain-Induced Arrhythmias in Single Isolated Myocardial Cells and in Cell Clusters In Vitro

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Abstract
Photoelectric recordings showed that single isolated mouse myocardial cells cultured in vitro developed various types of arrhythmias, such as fluttering and fibrillatory beatings on addition of ouabain. Cell clusters developed various types of arrhythmias on ouabain addition. At low concentrations of ouabain, beating of cell clusters as a whole was synchronous and rhythm of the synchronous beating was regular, but some component cells in clusters showed rhythmic contractions accompanied with faint, fibrillatory beating of high frequency. At intermediate concentrations of ouabain, beating of cell clusters as a whole was synchronous but the rhythm of the synchronous beating was irregular. Many component cells in the clusters showed irregular, strong contractions accompanied with faint, fibrillatory beating of high frequency. The irregular, strong contractions of 2 cells 60 .mu.m apart (4 cells apart) in the clusters were synchronous, but their faint, fibrillatory contractions were not. At high concentrations of ouabain, cell clusters as a whole stopped beating but many component cells in clusters showed asynchronous fibrillatory beating of high frequency. Photoelectric recordings showed that arrhythmias of component cells in cell clusters were essentially the same as those of single isolated myocardial cells. Ouabain-induced arrhythmias in single isolated myocardial cells and in cell clusters disappeared on quinidine sulfate addition. The genesis and recovery from ouabain-induced arrhythmias of cell clusters are explained as essentially due to the genesis and recovery from arrhythmias of individual component cells of the clusters.