CL 316,243, a selective beta(3)-adrenergic agonist, inhibits protein breakdown in rat skeletal muscle

The in vitro effect of CL 316,243 ( CL), a selective beta(3)-adrenoceptor agonist in the rate of overall proteolysis, the activity of proteolytic systems ( lysosomal, Ca2+- dependent, ATP-dependent, and ATP-independent) and in the process of protein synthesis was investigated in rat skeletal muscles. the rate of overall proteolysis in soleus muscle from rats incubated with CL ( 10(-4) and 10(-5) M) or epinephrine (10(-5) M) was significantly decreased. in vitro rates of maximal activity of Ca2+- dependent proteolysis in soleus muscles were decreased by about 41% in the presence of 10(-5) MCL. No change was observed in the activities of the lysosomal, ATP-dependent or ATP-independent proteolytic systems. the anti-proteolytic effect of CL or epinephrine was partially prevented by 10(-5) M SR 59230A, a selective beta(3)-adrenoceptor antagonist. the increase of proteolysis induced by food deprivation in soleus was abolished by in vitro addition of 10(-5) M CL. No change in proteolysis was observed in extensor digitorum longus (EDL) muscles incubated with any concentration of the beta(3)-adrenoceptor agonist tested. Rates of protein synthesis were not affected by 10(-4) M CL neither in soleus nor EDL. the data suggest that a beta(3)-adrenoceptormediated inhibition of Ca2+- dependent proteolysis participates of the antiproteolytic effect of catecholamines in oxidative muscles.Universidade Federal de São Paulo, Dept Physiol Biochem & Immunol, Sch Med, BR-14049900 São Paulo, BrazilSch Med Sao Jose Rio Preto, Dept Mol Biol, BR-15049900 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Physiol Biochem & Immunol, Sch Med, BR-14049900 São Paulo, BrazilWeb of Scienc