title: Sodium and potassium fluxes and membrane potential of human neutrophils: evidence for an electrogenic sodium pump.
abstract: Sodium and potassium ion contents and fluxes of isolated resting human peripheral polymorphonuclear leukocytes were measured. In cells kept at 37 degrees C, [Na]i was 25 mM and [K]i was 120 mM; both ions were completely exchangeable with extracellular isotopes. One-way Na and K fluxes, measured with 22Na and 42K, were all approximately 0.9 meq/liter cell water . min. Ouabain had no effect on Na influx or K efflux, but inhibited 95 +/- 7% of Na efflux and 63% of K influx. Cells kept at 0 degree C gained sodium in exchange for potassium ([Na]i nearly tripled in 3 h); upon rewarming, ouabain-sensitive K influx into such cells was strongly enhanced. External K stimulated Na efflux (Km approximately 1.5 mM in 140-mM Na medium). The PNa/PK permeability ratio, estimated from ouabain insensitive fluxes, was 0.10. Valinomycin (1 microM) approximately doubled PK. Membrane potential (Vm) was estimated using the potentiometric indicator diS-C3(5); calibration was based on the assumption of constant-field behavior. External K, but not Cl, affected Vm. Ouabain caused a depolarization whose magnitude dependent on [Na]i. Sodium-depleted cells became hyperpolarized when exposed to the neutral exchange carrier monensin; this hyperpolarization was abolished by ouabain. We conclude that the sodium pump of human peripheral neutrophils is electrogenic, and that the size of the pump-induced hyperpolarization is consistent with the membrane conductance (3.7-4.0 microseconds/cm2) computed from the individual K and Na conductances.
mesh_terms: D001693:Biological Transport, Active / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D009504:Neutrophils / Q000378:metabolism* / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D014634:Valinomycin; D010042:Ouabain; D012964:Sodium; D011188:Potassium