Effect of membrane potential on K-Cl transport in human erythrocytes.
We examined whether swelling-activated K-Cl cotransport is electrogenic in human erythrocytes. Baseline membrane potential, measured by the change in fluorescence of the carbocyanine dye diS-C3-5, was not different in hypotonically swollen (-7.6 mV) or isosmotically swollen cells (-9.5 mV). We used hemisodium, a new highly selective Na ionophore, in varying concentrations, in the presence of a fixed outwardly directed Na gradient (intracellular Na, 75 mM; external Na, 1 mM) to vary membrane potential over a wide range despite identical K and Cl concentrations. The membrane potential varied between -8 and -90 mV. K influx increased slightly with hyperpolarization in swollen and nonswollen cells. However, the difference between the two fluxes, swelling-activated K influx, a measure of K-Cl cotransport, was unaffected by voltage changes, as was swelling-activated K efflux. We conclude that K-Cl cotransport in human erythrocytes is electroneutral and by inference has a 1:1 stoichiometry.
Kaji
D M
DM
Renal Section, Veterans Affairs Medical Center, Bronx 10468.
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D052160:Benzothiazoles; D001692:Biological Transport; D002138:Calibration; D002232:Carbocyanines; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D005456:Fluorescent Dyes; D006400:Hematocrit; D006706:Homeostasis; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials; D011188:Potassium / Q000097:blood; D011189:Potassium Chloride / Q000097:blood*; D012964:Sodium / Q000097:blood
D052160:Benzothiazoles; D002232:Carbocyanines; D005456:Fluorescent Dyes; D007476:Ionophores; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C012944:3,3'-dipropyl-2,2'-thiadicarbocyanine; D011189:Potassium Chloride; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium