Asymmetric membrane expension and modification of active and passive cation permeability of human red cells by the fluorescent probe 1-anilino-8-naphthalene sulfonate

Abstract

1. 1. The membrane pertubations induced by the interaction of the fluorescent probe 1-anilino-8-naphthalene sulfonate (ANS) with human red blood cells were studied. 2. 2. ANS below 0.5 mM inhibits partially (20% maximum) the ouabain-insensitive Na + and K + influx and efflux. Above 0.5 mM ANS increases both Na + and K + leak fluxes. The increased cation leaks are larger for Na + than K +. 3. 3. The (Na ++K +)-ATPase and ouabain-sensitive Na + and K + fluxes are inhibited by ANS. Ouabain-insensitive, Mg 2+-dependent ATPase activity of ghosts is stimulated by [ANS] < 0.3 mM and inhibited by[ANS] > 0.3 mM. 4. 4. ANS also inhibits the Na +-dependent, ouabain-insensitive K + influx that is inhibited by ethacrynic acid and furosemide. 5. 5. Red blood cells become crenated with [ANS] < 0.1 mM and sphere at [ANS] > 1 mM. In the former conditions hypotonic hemolysis is decreased whereas the latter increase osmotic fragility. 6. 6. It is suggested that ANS expands the membrane asymmetrically by binding preferentially to the external membrane surface. 7. 7. It is concluded that ANS is a general inhibitor of ion transport, particularly of those processes thought to involve facilitated-diffusion mechanisms. The increased cation leaks observed at high ANS concentrations may be related to prehemolytic membrane disruption. 8. 8. The membrane pertubations caused by ANS are compared to those caused by other reversible inhibitors of anion exchange in red blood cells. Their possible modes of action are discussed.