Ouabain-induced arrhythmias of cultured myocardial cells and their improvement by quinidine.

Single-isolated myocardial cells obtained in vitro from fetal mouse heart developed various types of arrhythmic movements, such as fibrillatory and fluttering movements, in medium containing ouabain. The percentage of isolated myocardial cells that exhibited arrhythmic movements increased as ouabain concentration was increased. The arrhythmic movements induced by relatively low concentrations of ouabain were reduced by addition of quinidine. Cell clusters also developed various types of arrhythmic movements in medium containing ouabain. These arrhythmias became more severe when the ouabain concentration was increased. Under conditions such that approximately 43% of the single-isolated myocardial cells showed arrhythmias, many cells in cell clusters showed fibrillatory movements, but the cell clusters as a whole still maintained rhythmic beating. Under conditions in which about 65% of the single-isolated myocardial cells showed arrhythmias, cell clusters as a whole showed irregular beating. The cell clusters stopped beating under conditions in which about 79% of the single-isolated myocardial cells showed arrhythmias. Relatively mild types of arrhythmias of cell clusters were improved by addition of quinidine. From these observations, the genesis and improvement of arrhythmias of cell clusters were concluded to be essentially a result of the genesis and improvement of arrhythmic movements of the individual component cells in the clusters.