The Effect of Hemoglobin A and S on the Volume- and pH-Dependence of K-Cl Cotransport in Human Erythrocyte Ghosts

Abstract

K-Cl cotransport is abnormally active in erythrocytes containing positively charged hemoglobins such as Hb S (SS: beta6 Glu --> Val) or Hb C (CC: beta6 Glu --> Lys). The relatively younger age of erythrocytes in these diseases cannot completely account for the increased K-Cl cotransport activity. It has been suggested that these positively charged Hb may interact with the K-Cl cotransport system or one of its regulators and induce changes in its 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 in 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 normal erythrocytes decreases the magnitude of K-Cl cotransport and restores its volume dependency, but not its pH sensitivity. Addition of Hb S to WG from either normal or sickle erythrocytes restores the volume-dependent component of K-Cl cotransport and increases the magnitude of flux mediated by this transporter. Thus, Hb A and Hb S seem to affect in different manners the functional properties of K-Cl cotransport.

Perturbations of serum electrolyte levels in iron deficiency anemia - A comparative analysis

“…[21] Deoxygenation ) in sickle cells. [22] Luthra and Sears proposed that in β-thalassemia patients, oxidative damage induced by free globin chains has been implicated in the pathogenesis of the membrane abnormalities. He also mentioned that Na + , K + pump was reduced in thalassemialike cells, whereas it was increased in severe alpha-and betathalassemia cells.…”

KCl cotransport mediates abnormal sulfhydryl-dependent volume regulation in sickle reticulocytes

“…2,28 Nevertheless, there is evidence that the presence of sickle hemoglobin (Hb S, ␤ 6glu3val ) or hemoglobin C (Hb C, ␤ 6glu3lys ) directly affects the activity and properties of KCC in RBCs and RBC ghosts. [29][30][31]7 demonstrated acid stimulation of KCC in SS RBCs and showed that acidification of SS RBCs produced an increase in cell density. 6,7 Bookchin et al 32 showed that SS reticulocytes were susceptible to acid-induced dehydration and suggested that most of the dense cells in sickle blood arose from a subpopulation of SS reticulocytes with high sensitivity to KCC-mediated dehydration.…”

Erythrocyte Signal Transduction Pathways, their Oxygenation Dependence and Functional Significance

“…However, the volume-dependence of K-Cl cotransport on HbA and S in human erythrocyte ghosts suggests an alternative mechanism of participation of Hb in cell volume regulation [107]. K-Cl cotransport in white ghosts of human erythrocytes is volume-and pHindependent [107].…”