Beta-adrenoceptor antagonists and the release of creatine phosphokinase from hypoxic heart muscle

The ability of several beta-adrenoceptor antagonists with partial agonist activity (dl-oxprenolol, dl-acebutolol and dl-practolol) to attenuate the release of CPK that occurs during hypoxia (pO2 less than 0.8 kPa [6 MMHg]) has been studied and compared with the protection provided by dl-propranolol. dl-propranolol attenuated the hypoxic-induced release of CPK. The activity resided in the l isomer. dl-oxprenolol, acebutolol, and practolol were either less effective than propranolol in preventing CPK release, or they exacerbated the release. The protective effect of dl-propranolol extended to the hypoxic hyperthyroid heart but not to hearts that were perfused under aerobic (pO2 greater than 80 kPa [600 mmHg]) Ca2+-free conditions.