Adaptations of the beta-adrenoceptor-adenylyl cyclase system in rat skeletal muscle to endurance physical training
Nieto, J.L.; Diaz-Laviada, I.; Malpartida, J.M.; Galve-Roperh, I.; Haro, A.
Pflugers Archiv European Journal of Physiology 434(6): 809-814
1997
ISSN/ISBN: 0031-6768 PMID: 9306016 Document Number: 471162
beta-Adrenergic mechanisms may be important in the adaptation of skeletal muscle to endurance training. beta-Adrenergic signal transduction was examined in the gastrocnemius muscle of rats submitted to a progressive, 12-week treadmill running program and compared with sedentary controls. beta-Adrenoceptor density was significantly lower in exercised rats than in controls. The affinity constant for (125I)-(-) iodocyanopindolol binding was not different among the various groups. Adenosine cyclic monophosphate formation was significantly decreased in trained animals when isoproterenol plus guanosine triphosphate or forskolin plus Mn-2+ were used to stimulate adenylyl cyclase. Immunoblot analyses revealed that the amount of the alpha-subunit of stimulatory guanine nucleotide-binding protein (G-s,alpha), both the small and the large isoforms, also decreased with physical exercise. Thus, the present report shows that endurance training results in alterations in beta-adrenergic receptor density, adenylyl cyclase activity and G-s protein level in rat gastrocnemius muscle.