Oxidation induces a Cl(-)-dependent cation conductance in human red blood cells

Oxidative stress induces complex alterations of membrane proteins in red blood cells (RBCs) eventually leading to haemolysis. To study changes of membrane ion permeability induced by oxidative stress, whole-cell patch-clamp recordings and haemolysis experiments were performed in control and oxidised human RBCs. Control RBCs exhibited a small cation-selective whole-cell conductance (236 +/- 38 pS; n = 8) which was highly sensitive to the external Cl(-) concentration: replacement of NaCl in the bath by sodium gluconate induced an increase of this cation conductance by about 85 %. Exposing RBCs to t-butylhydroxyperoxide (1 mM for 10 min) induced a twofold increase in this cation conductance which was further stimulated after replacement of extracellular Cl(-) by gluconate, Br(-), I(-) or SCN(-). In addition, lowering the ionic strength of the bath solution by isosmotic substitution of NaCl by sorbitol activated the cation conductance. The Cl(-)-sensitive and oxidation-induced cation conductance was Ca(2+) permeable, exhibited a permselectivity of Cs(+) > K(+) > Na(+) = Li(+) >> NMDG(+), and was partially inhibited by amiloride (1 mM) and almost completely inhibited by GdCl(3) (150 microM), but was insensitive to TEA, BaCl(2), NPPB, flufenamic acid or quinidine. DIDS (100 microM) reversibly inhibited the activation of the cation conductance by removal of external Cl(-). Oxidation induced haemolysis in NaCl-bathed human RBCs. This haemolysis was attenuated by amiloride (1 mM) and inhibited by replacement of bath Na(+) by the impermeant cation NMDG(+). The Na(+)- and Ca(2+)-permeable conductance might be involved in haemolytic diseases induced by elevated oxidative stress, such as glucose-6-phosphate dehydrogenase deficiency.