Effect of propranolol and pindolol on the up-regulation of lymphocytic beta adrenoceptors during acute submaximal physical exercise. A placebo-controlled double-blind study.

The effect of beta-adrenoceptor antagonists, with and without intrinsic sympathomimetic activity, on the regulation of lymphocytic beta adrenoceptors during acute physical exercise was studied. Seven healthy volunteers underwent a graded maximal ergometer test after treatment for 7 days with placebo, propranolol (2 x 80 mg/day), or pindolol (2 x 10 mg/day). Each subject received the three types of drug treatment in a double-blind, randomized fashion, with 3 weeks wash-out periods between the on-drug periods. The mean resting density of lymphocytic beta adrenoceptors was 46 +/- 5 fmol/mg protein (mean +/- SEM) during placebo, 53 +/- 5 fmol/mg protein during propranolol, and 29 +/- 4 fmol/mg protein during pindolol treatment (p less than 0.05, pindolol vs. propranolol). Exercise induced a significant up-regulation of the beta-adrenoceptor density during each treatment modality, but the increment was attenuated during propranolol (mean elevation, 16 +/- 2 fmol/mg protein, p less than 0.05) and pindolol intake (13 +/- 4 fmol/mg protein, p less than 0.02) as compared with the placebo value (56 +/- 13 fmol/mg protein). Moreover, exercise-induced increment of lymphocytic cyclic AMP (cAMP) production was virtually abolished by the two beta-adrenoceptor antagonists. In conclusion, administration of beta-adrenoceptor antagonists is associated with a subnormal up-regulation of the lymphocytic beta-adrenoceptors and alterations in their functioning during heavy physical effort. This attenuation is not modified by intrinsic sympathomimetic activity of the compound.