By means of physiological, electron microscopical and histochemical methods, changes in intensity of mechanisms participating in calcium transport and the cations localization in cardiomyocytes have been studied, the changes resulted from an emotional-painful stress. After the stress, the contractile function of the rat isolated heart becomes more dependent on calcium concentration in the perfusate. As demonstrate combined electron microscopical and histochemical methods and, first of all, determination of calcium antimonate in the cardiomyocytes, together with increased cardiac function, an elevated amount of calcium localized in sarcoplasm of cardiomyocytes is observed, especially in the subsarcolemmic area. The data obtained demonstrate that the membrane mechanisms of calcium transport are injured and calcium content in the sarcoplasm is increased; that can play a definite role in the development of focal lesions in the myocardium at a stress.