Effect of propranolol on the metabolism and function of the rat heart
The effect of propranolol, a beta-adrenergic blocking agent, was studied on the metabolism and function of the isolated, perfused rat heart. Propranolol (20 μm) depressed the oxygen consumption, coronary flow rate, palmitate uptake and oxidation as well as the high energy phosphate contents of the perfused heart. Propranolol significantly reduced heart rate while the time to peak height of developed tension period was increased. The effect of propranolol was also studied on the metabolism of heart muscle slices and the sarcosomal oxidative phosphorylation process. With pyruvate or glucose as substrate, propranolol stimulated the respiration and metabolism of heart slices, while it depressed oxidative phosphorylation. In order to eliminate the effect of the reduction in heart rate on substrate metabolism in the perfused heart, additional studies were performed in which the effect of propranolol was studied in hearts driven at a controlled heart rate, by a pacemaker. The results showed that the chronotropic effect of propranolol had a significant effect on the reduction in substrate metabolism. © 1971.