Reduced Sodium Concentration and Increased Sodium-Potassium Pump Activity of Erythrocytes

transport) were measured in whole blood of 16 normotensive and 19 hypertensive white male subjects, within seconds or minutes after withdrawal of blood. Erythrocyte Na, and Na/K, were reduced (p<0.05), and ouabain-sensitive ^Rb uptake was increased (p<0.01) in hypertensive subjects. In a separate group of hypertensive white male subjects, an inverse correlation was found between eryth-rocyte Na/Ki and ouabain-binding sites per erythrocyte (r = 0.85, p<0.01, n = 9). The abnormalities of erythrocyte cation fluxes in hypertensive subjects are similar to those induced by aldosterone in vascular smooth muscle cells and by glucocorticoid administration in the erythrocytes of human subjects, suggesting similarities in pathogenesis. (Hypertension 9 [Suppl III]: 111-13—111-18, 1987) KEY WORDS binding intracellular sodium • potassium • rubidium-86 uptake • [3H]ouabain A BNORMALITIES of all the major erythrocyte / \ Na transport systems have been reported in A. \- human hypertension. '•2 With the exception of an increased Na-Li countertransport system, which un-der physiological conditions does not mediate any transport of Na across cell membranes, the results have been contradictory. Several investigators have report-ed increased activity of the ouabain-sensitive Na+-K+ pump, but others could not confirm this finding.2"5 The activity of the Na+-K+ cotransport system has been reported as reduced, increased, and unchanged. '•6 The net effect of these abnormalities in Na fluxes on the transmembrane Na gradient of red blood cells (RBCs) in human hypertension is uncertain. There have been reports of increased and unchanged erythrocyte Na content in human hypertension.7"9 The two main reasons for these contradictory find-ings appear to be the genetic heterogeneity of the dis-ease and methodological problems.1'10 ' " The genetic aspects of erythrocyte cation transport are under inves