INHIBITORY EFFECT OF AMILORIDE ON GLUCOSE-TRANSPORT IN ISOLATED RAT ADIPOCYTES

The effect of amiloride on 3-O-methylglucose (3-O-MG) uptake was studi ed in isolated rat adipocytes to define to what extent amiloride inhib ited the process of insulin action or glucose transport. Amiloride (1 mM), which did not change the intracellular water space of adipocytes, inhibited by 43.3% the insulin-stimulated uptake of 3-0-MG, while it did not appear to inhibit the basal uptake. To distinguish the inhibit ory effect on glucose transport activity from that on the process of i nsulin action, the effect of amiloride was evaluated in the transport system using adipocytes deprived of ATP, in which glucose transporters were considered immobile. Amiloride (1 mM) inhibited th's transport b y 32.8% in an insulin-stimulated state, which was obtained using adipo cytes that had been treated with 20 nM insulin and exposed to 2 mM KCN , whereas it did not inhibit the transport system at the basal state. In the inhibitory effect, 76% was thus attributable to the inhibition of glucose transport activity recruited by insulin and 24% to the inhi bition of the action of 20 nM insulin itself. These results indicate t hat amiloride can not be used as a specific inhibitor of the insulin a ction itself.