The effect of hemoglobin A and S on the volume- and pH-dependence of K-Cl cotransport in human erythrocyte ghosts

K-Cl cotransport is abnormally active in erythrocytes containing positively charged hemoglobins such as Hb S (SS: beta 6 Glu --> Val) or Hb C (CC: bet a 6 Glu --> Lys). The relatively younger age of erythrocytes in these disea ses cannot completely account for the increased K-Cl cotransport activity. It has been suggested that these positively charged Hb may interact with th e K-Cl cotransport system or one of its regulators and induce changes in it s functional activity. We report here data on the volume- and pH-dependence of K-Cl cotransport in ghosts obtained from normal and sickle erythrocytes , and on the effect of addition of either Hb A or Hb S before resealing. In erythrocyte ghosts prepared with the gel column method to contain minimal amounts of Hb, (white ghosts, WG), K-Cl cotransport has similar magnitude i n normal and sickle erythrocytes, is not inhibited by alkaline pH and it is volume-independent. Addition of low concentrations of Hb A to WG from norm al erythrocytes decreases the magnitude of K-Cl cotransport and restores it s volume dependency, but not its pH sensitivity. Addition of Hb S to WG fro m either normal or sickle erythrocytes restores the volume-dependent compon ent of K-Cl cotransport and increases the magnitude of flux mediated by thi s transporter. Thus, Hb A and Hb S seem to affect in different manners the functional properties of K-Cl cotransport.