Catecholamines inhibit Ca(2+)-dependent proteolysis in rat skeletal muscle through beta(2)-adrenoceptors and cAMP.
Overall proteolysis and the activity of skeletal muscle proteolytic systems were investigated in rats 1, 2, or 4 days after adrenodemedullation. Adrenodemedullation reduced plasma epinephrine by 95% and norepinephrine by 35% but did not affect muscle norepinephrine content. In soleus and extensor digitorum longus (EDL) muscles, rates of overall proteolysis increased by 15-20% by 2 days after surgery but returned to normal levels after 4 days. The rise in rates of protein degradation was accompanied by an increased activity of Ca(2+)-dependent proteolysis in both muscles, with no significant change in the activity of lysosomal and ATP-dependent proteolytic systems. In vitro rates of Ca(2+)-dependent proteolysis in soleus and EDL from normal rats decreased by ~35% in the presence of either 10(-5) M clenbuterol, a beta(2)-adrenergic agonist, or epinephrine or norepinephrine. In the presence of dibutyryl cAMP, proteolysis was reduced by 62% in soleus and 34% in EDL. The data suggest that catecholamines secreted by the adrenal medulla exert an inhibitory control of Ca(2+)-dependent proteolysis in rat skeletal muscle, mediated by beta(2)-adrenoceptors, with the participation of a cAMP-dependent pathway.
Navegantes
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LC
Department of Physiology and Biochemistry, School of Medicine, University of São Paulo, Ribeirão Preto, 14049-900 São Paulo, Brazil.
Resano
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Migliorini
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RH
Kettelhut IC
D000313:Adrenal Medulla / Q000502:physiology / Q000601:surgery; D058666:Adrenergic beta-2 Receptor Agonists; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002395:Catecholamines / Q000494:pharmacology* / Q000502:physiology; D002976:Clenbuterol / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D010450:Endopeptidases / Q000378:metabolism; D004837:Epinephrine / Q000032:analysis / Q000097:blood; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000032:analysis / Q000097:blood; D051381:Rats; D017208:Rats, Wistar; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects / Q000502:physiology*
D058666:Adrenergic beta-2 Receptor Agonists; D002395:Catecholamines; D009124:Muscle Proteins; D018343:Receptors, Adrenergic, beta-2; D003994:Bucladesine; D000242:Cyclic AMP; D010450:Endopeptidases; D002118:Calcium; D009638:Norepinephrine; D002976:Clenbuterol; D004837:Epinephrine