Glycogen Concentration in Working and Nonworking Ventricles of Isolated Dog Hearts

Abstract

Glycogen utilization in working and nonworking ventricles was studied at high (over 70 mg/100 ml) and low (27 to 61 mg/100 ml) arterial glucose concentrations and after insulin or epinephrine addition in 16 isolated ventricle preparations of dog hearts. Coronary perfusion and hemodynamic determinants of right ventricular work were controlled, and the left ventricle was kept unloaded. Time courses of change in ventricular glycogen concentration were determined during monitoring of heart rate, workload, arterial oxygen saturation, and coronary perfusion pressure. Epicardial samples for glycogen analysis were taken from each ventricle, and glucose uptake from circulating blood was determined. Glycogen loss was greater in working right than in nonworking left ventricles. In spontaneously fibrillating hearts, this difference was not observed, and there was greater glycogenolysis than during coordinated contraction. Insulin administration early in experiments led to equivalent glycogen loss in working right and nonworking left ventricles. There was glycogen preservation in both ventricles of fibrillating hearts. Epinephrine augmented glycogen loss in fibrillating hearts; depletion was never complete. Myocardial glucose uptake, corrected for red cell glycolysis, was proportional to initial arterial glucose concentration.