Catecholamines inhibit insulin-stimulated glucose transport in adipocytes, in the presence of adenosine deaminase.

Epinephrine, norepinephrine and isoproterenol completely inhibited insulin-stimulated 2-deoxyglucose uptake by rat adipocytes, but only when adenosine was prevented from accumulating in the incubation medium by addition of adenosine deaminase. Basal uptake rates were not affected. The effects were not observed in the presence of adenosine deaminase plus N6-phenylisopropyl adenosine (a non-metabolizable adenosine analogue), suggesting that it is the lowered adenosine level rather than the presence of the enzyme itself which allows the catecholamines to inhibit insulin action. The inhibitory effects of the catecholamines were blocked by propranolol but not phentolamine, suggesting that they are mediated via beta-adrenergic receptors.