EFFECT OF THE ANION TRANSPORT INHIBITOR SITS OF THE VOLUME-DEPENDENT NA+ H+ EXCHANGE IN RAT ERYTHROCYTES/

Using ethyl isopropyl amiloride (EIPA), a more selective Na+/H+ exchan ge inhibitor than amiloride, we supported the stimulation of the excha nger in rat erythrocytes during the hyper- and isoosmotic shrinking by , respectively, sucrose and valinomycin. Shrinking inhibits (ouabain bumetanide + EIPA)-insensitive SITS-inhibited influx of Na-22+ presum ably mediated by band 3 protein. Stimulation of Na+/H+ exchange during the isoosmotic shrinking was 4-5 times as high as at the hyperosmotic shrinking (300 mM sucrose). SITS (100 muM) did not eliminate these di fferences. It is concluded that the buffering activity of anion transp ort in rat erythrocytes does not limit the volume-stimulated Na+/H+ ex change.