The effects of the vitamin A lysosomal membrane labilizator on electrophysiological characteristics was investigated on frog cardiomyocytes. Large and small doses of vitamin A produced qualitatively identical effects: decrease of the steepness of action potential (AP) front, decrease of the spike amplitude, shortening of the plateau, decrease of the steepness in the last phase of AP-repolarization. The AP-duration decreased considerably. Large doses of the vitamin also reduced the rest potential level and insignificantly increased the heart contractions frequency. We assume that vitamin A can affect the cardiomyocyte surface membrane permeability, thereby decreasing its excitability due to suppression of the sodium and potassium.