Nieto J L, Diaz-Laviada I, Malpartida J M, Galve-Roperh I, Haro A
Departamento de Bioquímica y Biología Molecular I, Fac. C.C. Químicas, Universidad Complutense, E-28040 Madrid, Spain.
Pflugers Arch. 1997 Nov;434(6):809-14. doi: 10.1007/s004240050469.
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 Mn2+ were used to stimulate adenylyl cyclase. Immunoblot analyses revealed that the amount of the alpha-subunit of stimulatory guanine nucleotide-binding protein (Gs,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 Gs protein level in rat gastrocnemius muscle.
