[The effect of insulin on cardiac activity and on the coronary and systemic circulations]

The studies were performed on healthy closed-chest chloralose-anaesthetized dogs using catheterization, extracorporal perfusion and resistography of coronary arteries and catheterization and continuous drainage of the coronary sinus. Insulin (0.1 and 1.0 IU/kg, i.v.) injected to healthy animals produced dose-dependent biphasic cardiohaemodynamic reactions. The first phase of the reaction includes transient (5-10 min) cardiac function strengthening, coronary arteries constriction, heart rate acceleration, myocardial oxygen consumption elevation, coronary sinus blood pH elevation and pO2 decrease. After that there arises more prolonged and constant dilation of coronary arteries reduction of the cardiac function, slowing of the heart rate, lowering of the myocardial oxygen consumption, decrease of cardiac venous blood pH and increase of pO2, reduction of T waves magnitude and ST segments shifts both in standard and breast leads. The second phase of the reaction is either attenuated or even absent after blockade of beta-adrenoceptors (propranolol, 0.5 mg/kg, i.v.). The results indicate that insulin effects on cardiohaemodynamics are realized through the interaction between insulin and heart and vessels of the adrenergic system.