title: Counter-regulation of insulin-stimulated glucose transport by catecholamines in the isolated rat adipose cell.
abstract: The interaction between catecholamines and insulin in regulating glucose transport in isolated rat adipose cells has been evaluated. In the absence of insulin, 1 microM isoproterenol stimulates 3-O-methylglucose transport approximately 2-fold. However, isoproterenol in combination with adenosine deaminase inhibits glucose transport activity approximately 60%. N6-Phenylisopropyladenosine, a nonmetabolizable adenosine analogue, substantially reverses this inhibitory effect and actually stimulates glucose transport activity approximately 2-fold in the absence of isoproterenol. Dibutyryl cAMP inhibits glucose transport activity approximately 75% regardless of adenosine deaminase. While none of these agents significantly influences the basal concentration of plasma membrane glucose transporters, as assessed by specific D-glucose-inhibitable cytochalasin B binding, isoproterenol or dibutyryl cAMP in combination with adenosine deaminase reduces that in the low density microsomes 19 and 58%, respectively. In the presence of insulin, both isoproterenol and adenosine deaminase alone inhibit glucose transport activity approximately 25%. However, only the latter is accompanied by a corresponding decrease in the insulin-stimulated concentration of plasma membrane glucose transporters. Together, isoproterenol and adenosine deaminase inhibit insulin-stimulated glucose transport activity approximately 75%, even in the presence of 5 mM glucose to maintain cellular ATP levels. A similar inhibition is observed with dibutyryl cAMP. However, these agents decrease the insulin-stimulated concentration of plasma membrane glucose transporters only approximately 45%. Nevertheless, all of these inhibitory effects occur through decreases in the transport Vmax. In addition, N6-phenylisopropyladenosine partially reverses the inhibitory effects induced by the presence of adenosine deaminase. These results suggest that catecholamines counter-regulate basal and insulin-stimulated glucose transport in rat adipose cells through a cAMP-mediated mechanism, but only in part by modulating the translocation of glucose transporters.
mesh_terms: D019325:3-O-Methylglucose; D000243:Adenosine Deaminase / Q000378:metabolism; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D010660:Phenylisopropyladenosine / Q000494:pharmacology; D051381:Rats
chemical_list: D007328:Insulin; D008757:Methylglucosides; D008759:Methylglycosides; D019325:3-O-Methylglucose; D010660:Phenylisopropyladenosine; D003994:Bucladesine; D000243:Adenosine Deaminase; D007545:Isoproterenol