Metabolism of the perfused rabbit heart. IV. Effects of beta-adrenergic blockade on enzyme release and later energy stores during postanoxic reoxygenation.

The effects of 80 microM dl-propranolol on left ventricular (LV) performance, energy stores, and creatine kinase (CK) release were studied in a modified Langendorff rabbit heart preparation during 75 min of aerobic perfusion and postanoxic reoxygenation. The data showed that this concentration of propranolol, which blocked the effects of beta-adrenergic stimulation without affecting LV performance, coronary sinus flow (CSF), or oxygen consumption (MV O2), was associated with greater stores of glycogen and adenine nucleotides at the end of aerobic perfusion. Similar effects were observed during postanoxic reoxygenation, when recoveries of left ventricular systolic pressure, heart rate, heart rate--left ventricular systolic pressure product, CSF, and MV O2 remained unchanged during propranolol administration, but myocardial concentrations of glycogen, creatine phosphate, and ATP were greater and the ATP:AMP ratio and the energy charge were higher than in untreated hearts. In addition, the rate of CK loss was lower in the blocked postanoxic hearts than in the unblocked group. These results indicate that propranolol had a beneficial effect on cardiac metabolism during postanoxic recovery tending to normalize energy stores and to reduce enzyme loss during reoxygenation or perfused rabbit hearts without affecting mechanical performance, coronary flow, or O2 metabolism.