Effect of extracellular potassium concentration on the sodium-potassium pump rate in human lymphocytes.
1. The purpose of this study was to determine whether physiological changes in extracellular free [K+] cause significant changes in the Na(+)-K+ pump rate and intracellular free [Na+]. 2. The Na(+)-K+ pump rate was measured in human lymphocytes by determining ouabain-sensitive 86Rb+ influx at several concentrations of K+. The Na(+)-K+ pump rate increased within the physiological range of extracellular free [K+] (K1/2 = 1.5 mmol/l). 3. To test the hypothesis that elevation of extracellular free [K+] reduces intracellular free [Na+] rapidly, which in turn then slows the pump rate during experimental incubations, lymphocyte intracellular free [Na+] was measured using the fluorochrome sodium-binding benzofuran isophthalate. With larger elevations of extracellular free [K+], intracellular free [Na+] dropped more rapidly. Thus previous discrepancies among determinations of K1/2 may be the result of variations in incubation times, which can skew the pump rates measured during incubations in various extracellular free [K+] values. Steady-state intracellular free [Na+] varied inversely with extracellular free [K+].
Webb
G D
GD
Department of Molecular Physiology and Biophysics, University of Vermont, College of Medicine, Burlington 05405, USA.
Taylor
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EA
Oh
V M
VM
Yeo
S B
SB
Ng
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LL
D000328:Adult; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000378:metabolism*; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D012414:Rubidium Radioisotopes; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium