The effect of deoxygenation on whole-cell conductance of red blood cells from healthy individuals and patients with sickle cell disease

Red blood cells from patients with sickle cell disease (SCD) exhibit increased electrogenic cation permeability, particularly following deoxygenation and hemoglobin (Hb) polymerisation. This cation permeability, termed P-sickle, contributes to cellular dehydration and sickling, and its inhibition remains a major goal for SCD treatment. Nevertheless, its characteristics remain poorly defined, its molecular identity is unknown, and effective inhibitors have not been established. Here, patch-clamp methodology was used to record whole-cell currents in single red blood cells from healthy individuals and patients with SCD. Oxygenated normal red blood cells had a low membrane conductance, unaffected by deoxygenation. Oxygenated HbS cells had significantly increased conductance and, on deoxygenation, showed a further rise in membrane conductance. The deoxygenation-induced pathway was variable in magnitude. It had equal permeability to Na+ and K+, but was less permeable to NMDG(+) and Cl-. Conductance to Ca2+ was also of a similar magnitude to that of monovalent cations. It was inhibited by DIDS (100 mu M), Zn2+ (100 mu M), and by Gd3+ (IC50 of approximately 2 mu M). It therefore shares some properties with P-sickle. These findings represent the first electrical recordings of single HbS cells and will facilitate progress in understanding altered red blood cell cation transport characteristics of SCD.