It has been shown that apressin in doses of 0.5 and 1 mg/kg intravenously prevented a drop of the amplitude of the left ventricular pressure, pressure, maximal speed of its rise and relaxation which developed in control experiments on dogs after ligation of the coronary artery. Apressin increased the volumetrical rate of the collateral coronary blood flow, diminished peripheral vascular resistance in the zone of myocardial ischemia and reduced the ST segment of the heart epicardial electrogram. The drug lowered glucose consumption, lactate content, and "excess' lactate in blood samples collected from the ischemic zone. At succinate and glutamate oxidation, it decreased oxygen consumption by mitochondria from the myocardial ischemic zone in the acceptor-free system, and increased the respiration stimulation coefficient, the respiratory control alccording to Change being improved at glutamate oxidation.