Propranolol attenuates exercise-induced increment in human lymphocytic beta-adrenergic receptors.

The effect of peroral propranolol administration on the level of lymphocytic beta-adrenergic receptors was studied in six healthy volunteers using an acute exercise test. When no drug was used, a 15-min ergometer exercise period induced a significant increase in the receptor density (from 42 +/- 5 to 117 +/- 14 fmol/mg protein; mean +/- SEM), followed by a return to the pre-exercise level after a 1-hr rest. During propranolol administration (40 mg, three times daily), the basal receptor level (49 +/- 4 fmol/mg protein) did not change but the exercise-induced increment of the receptor density was significantly inhibited (peak value 79 +/- 5 fmol/mg protein, p less than 0.05). This effect could not be explained by direct competition for receptor binding sites by propranolol nor by differences in the plasma adrenalin and noradrenaline concentrations during the two tests. The fact that propranolol interferes with the normal adaptation of the beta-adrenergic receptor level to acute exercise may explain some of the adverse effects of beta-blocking drugs on physical performance.