title: The influence of pH and membrane potential on passive Na+ and K+ fluxes in human red blood cells.
abstract: Passive (ouabain-insensitive) Na+ and K+ effluxes from human red blood cells were measured over the range pHo 6.2-8.5. On raising pHo, Na+ efflux increased and this was mainly attributable to the piretanide-sensitive component: K+ efflux likewise but attributable to both piretanide-sensitive and piretanide-insensitive components. On replacing Cl- with non-penetrating anions (mainly gluconate), Na+ and K+ effluxes increased, mostly attributable to the piretanide-insensitive components. On restoring pHi either by reducing pHo or by applying DIDS, the influence of pHo on Na+ and K+ effluxes was diminished. These results suggest that pHi rather than Em is the dominant influence. Passive Na+ and K+ effluxes and influxes in the presence of bumetanide were tested fro conformity to the Ussing independence relationship. For K+, the calculated and observed ratios agreed, indicating that the sodium pump, 'cotransport' and leak wholly account for K+ fluxes in human red blood cells. For Na+, the ratios did not agree and a 1:1 Na+/Na+ exchange did not account for the discrepancy. Pathways for Na+ appear to be more numerous than for K+.
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000328:Adult; D000838:Anions / Q000097:blood; D002034:Bumetanide / Q000097:blood; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008433:Mathematics; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012964:Sodium / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D000838:Anions; D013449:Sulfonamides; D002034:Bumetanide; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D010042:Ouabain; D012964:Sodium; C015451:piretanide; D000254:Sodium-Potassium-Exchanging ATPase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium