Additive effects of norepinephrine and cyclic AMP on the activation of the protein kinase from adipose tissue.
In this work the kinetics of activation of the cyclic AMP-dependent protein kinase by several catecholamines and ACTH, have been studied in rat epididymal fat pads and isolated fat cells. The method of Soderling and co-workers which permits the measurement of the state of activation of the protein kinase after hormonal stimulation in adipose tissue, has been used. Kinetics experiments where norepinephrine was used showed that the results obtained with isolated cells conform to the models of Sutherland and Brostrom and co-workers. Wtih intact tissue, norepinephrine not only stimulates the protein kinase activity measured without exogenous cyclic AMP but also the total activity measured in the presence of cyclic AMP (5 X 10(-6) M); thus the effect of norepinephrine, obtained during incubation of the tissue, and that of cyclic AMP, added to the soluble fraction after incubation, were additive. This effect seems to be of the beta type because it is blocked completely by propranolol. A weak, additive but significant effect was also obtained with epinephrine and isoproterenol but not with ACTH. Neither cyclic GMP nor cyclic IMP seems implicated in this effect. It was shown that stroma vascular cells which are present in the fat pads are not involved. These results suggest that the effects of norepinephrine on the protein kinase of the fat pads cannot be completely explained by the model of Brostrom and colleagues.
D000273:Adipose Tissue / Q000187:drug effects / Q000201:enzymology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D011494:Protein Kinases; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine