Amiloride-sensitive sodium–hydrogen exchange in osmotically shrunken rabbit red blood cells

in osmotically shrunken rabbit red blood cells. Am. J. Physiol. 251 (Cell Physiol. 20): C32-C40, 1986.-As part of a detailed study of cell volume regulation in high-potassium mammalian erythrocytes, we have characterized ouabain-insensitive sodium transport in normal and osmotically shrunken rabbit red cells. In cells of normal volume and physiological pH, there is no amiloride-inhibited component of the sodium efflux (into either sodium-containing or sodium-free media). Osmotic shrinkage activates an amiloride-sensitive (50 % inhibitory concentra-tion = lo- ” M) sodium transport system that can catalyze net sodium movement in either direction. This system appears to be distinct from the sodium-sodium (sodium-lithium) counter-transporter that operates in cells of normal volume. Replace-ment of chloride with acetate does not inhibit the sodium flux, but replacement with either nitrate or thiocyanate is inhibitory