[Increase in the lymphocyte beta-adrenergic receptor population during physical exercise].
The risk of cardiac arrhythmias during exercise and the recovery period may be enhanced by sympathetic activity. Accordingly, lymphocyte beta-adrenoceptor density was measured in 5 healthy men, aged between 25 and 32 years, at rest, at peak exercise and during the recovery period. Exercise increased 3H-dihydroalprenolol binding from 125 +/- 58 to 234 +/- 70 fmol/mg protein (p less than 0.02). During recovery, beta-adrenoceptor density was still higher than at rest, being 192 +/- 36 fmol/mg protein (p less than 0.02). No significant difference was found between exercise and recovery values (Tab. I). Results did not change when binding data were standardized to lymphocyte number, thus demonstrating that increases in binding were independent of exercise-induced lymphocytosis. Kd did not change significantly during the study. Since lymphocytic beta-adrenoceptor density may parallel myocardial beta-adrenoceptor density, this study suggests the myocardium may be more sensitive to the arrhythmogenic properties of catecholamines during exercise.