Chloride conductance and volume-regulatory nonselective cation conductance in human red blood cell ghosts

To identify the ion channels involved in erythrocyte volume regulation, whole-cell currents from human red blood cells (RBCs) were recorded in isotonic, hypotonic and hypertonic media. In isotonic NaCl bath solution, whole-cell currents rectified outwardly with reversal potentials (V-rev) between the equilibrium potential of Cl- (E-Cl) and that of nonselective cations (NSC), E-NSC. Replacement of bath Cl- by gluconate decreased outward conductance (C-outward) by 43+/-6% (n=5) and shifted V-rev with E-Cl indicating a high fractional Cl- conductance. hypotonic cell swelling reversibly decreased G(outward) by 23+/-3% (n=8) while hypertonic cell shrinkage reversibly increased Goutward by 27+/-8% (n=5). These shrinkage-activated and swelling-inactivated current fractions rectified outwardly with I:,, at ENSC suggesting that both fi actions are generated by the same type of NSC channel. The shrinkage-activated activated decreased from 4.7+/-1.2 nS (n=3) to 1.4+/-0.4 nS (n=5) and 0.5+/-0.4 nS (n=7) with the increase of pipette [Cl-] from 7 mM to 39 mM and 139 mM, respectively. Similarly, with this increase of pipette [Cl-], Goutward under isotonic control conditions decreased from 8.2+/-1.4 nS (n=5) to 7.4+/-1.0 nS (n=20) and 4.1+/-0.7 nS (n=17), due to the differing activity of these NSC channels. In conclusion, human RBCs express, besides a high fractional Cl- conductance, NSC channels that are regulated by cell volume and the cytosolic [Cl-].