The interaction between catecholamines and insulin in regulating glucose transport in isolated rat adipose cells has been evaluated. In the absence of insulin, 1 μM isoproterenol stimulates 3-O-methylglucose transport ~2 fold. However, isoproterenol in combination with adenosine deaminase inhibits glucose transport activity ~60%. N6-Phenylisopropyladenosine, a nonmetabolizable adenosine analogue, substantially reverses this inhibitory effect and actually stimulates glucose transport activity ~2-fold in the absence of isoproterenol. Dibutyryl cAMP inhibits glucose transport activity ~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 ~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 ~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 ~45%. Nevertheless, all of these inhibitory effects occur through decreases in the transport V(max). 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.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|State||Published - Jan 1 1984|
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology