INSULIN MODULATION OF NA H ANTIPORT IN RAT RED-BLOOD-CELLS/

Red blood cells have been Shown to possess specific insulin receptors, with characteristics similar to the receptors of typical target cells . The present work was carried out to study the modulation of maloidea e sensitive Na/H antiport by insulin on rat red blood cells. The activ ity of the Na/H antiport was determined by a new technique which invol ves the measurement of the fluorescence of 2',7'-bis(2-carboxyethyl)-5 ,6-carboxyfluorescein (BCECF) loaded rbc's as function of their intrac ellular pH (pHi). Our results show that the antiport in red blood cell s displays the same behaviour as in other cells and it is inhibited by amiloride. Insulin stimulates the antiport with a dose-dependence sim ilar to other typical insulin effects: a maximum at 10 nM and a smalle r effect at higher and lower hormone concentrations. Insulin effect on the antiport was completely abolished by amiloride (0.1 mM) and signi ficantly inhibited by ouabain (1 mM) showing, also in red blood cells, the strict dependence of the Na/H antiport on the. functioning of the Na pump.