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 (Vrev) between the equilibrium potential of Cl- (ECl) and that of nonselective cations (NSC), ENSC. Replacement of bath Cl by gluconate decreased outward conductance (G outward) by 43 +/- 6% (n = 5) and shifted Vrev with ECl indicating a high fractional Cl- conductance. Hypotonic cell swelling reversibly decreased G outward by 23 +/- 3% (n = 8) while hypertonic cell shrinkage reversibly increased G outward by 27 +/- 8% (n = 5). These shrinkage-activated and swelling-inactivated current fractions rectified outwardly with Vrev at ENSC suggesting that both fractions are generated by the same type of NSC channel. The shrinkage-activated deltaG outward 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-], G outward 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-].
Huber
S M
SM
Department of Physiology, University of Tuebingen, Germany. stephan.huber@uni-tuebingen.de
Gamper
N
N
Lang
F
F
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D048429:Cell Size; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004553:Electric Conductivity; D017097:Electric Impedance; D004910:Erythrocyte Membrane / Q000502:physiology*; D005942:Gluconates / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007038:Hypotonic Solutions; D008564:Membrane Potentials; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride; D012996:Solutions
D018118:Chloride Channels; D002712:Chlorides; D005942:Gluconates; D007038:Hypotonic Solutions; D012462:Saline Solution, Hypertonic; D012996:Solutions; D012965:Sodium Chloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C030691:gluconic acid