Effects of propranolol on β- Adrenergic receptor of experimental acute myocardial infarction in rats

By using receptor autoradiography to observe the distribution and density of receptors, the effects of propranolol, a β-blocker, on β-adrenergic receptor of experimental acute myocardial infarction (AMI) were studied. One week after ligation of proximate left anterior descend (LAD) coronary artery, [3H] DHA binding sites were markedly decreased in both infarctregion and non-infarct region. After treatment of propranolol (100 μg/kg), the [3H] DHA binding sites were obviously increased in the infarct region, and they were further decreased in the non-infarct region. The ratio of [3H] DHA binding sites of the infarct region to non-infarct region was from 0. 24 at LAD ligation to 0. 87 after propranolol treatment, which was close to 0. 97 of control group (sham operation). The results indicated that the propranolol acted directly on myocardial β- adrenergic through the receptor regulation of the balance of β-receptors between the infarct region and non-infarct region, and improvement of the myocardial consonation and contraction synergism, thereby protecting the heart affected by AMI.