NEITHER PHYSICAL EXERCISE NOR ALPHA(1)-ADRENERGIC-BLOCKADE AND BETA-ADRENERGIC-BLOCKADE AFFECT PLASMA ENDOTHELIN CONCENTRATIONS

Endothelins (ET) are recently discovered vasoconstrictor agents releas ed from endothelial cells and have been the object of intense investig ation by researchers. Many of the factors that seem to influence the r elease of ET are modified by prolonged exercise. The purpose of this s tudy was to investigate the effect of physical exercise on ET plasma c oncentrations and the effect of alpha- and beta-blockade on ET concent rations at rest and during exercise. Fifteen young volunteers (age 20- 35 years) performed an exercise test on a bicycle ergometer. The start ing workload of 50 W was increased by 30 W every 3 min until maximal h eart rate was achieved; after a 2 min recovery period at 50 W the test continued for 15 min at 60% maximal work load. Blood samples were tak en for ET determination before and after the test After 1 week, the te st was repeated, In the 2 days before either the first or the second t est, each volunteer randomly received carvedilol (C) (25 mg), an alpha (1)-adrenoceptor and beta-adrenoceptor blocker. There was no significa nt difference in ET concentrations after exercise with or without C ad ministration (1.24 +/- 0.66, 1.42 +/- 0.83, 1.66 +/- 1.15, 1.61 +/- 0. 87 pg/mL), showing that prolonged aerobic exercise does not affect pla sma ET levels. Moreover, in our healthy young volunteers, blockade of alpha- and beta-adrenoceptors had no effect on ET levels at rest and a fter exercise.