Plasma Sodium Pump Inhibitor in Essential Hypertension and Normotensive Subjects with Hypertensive Heredity

Abstract

The presence in plasma extracts of a sodium pump inhibitor with digitalis-like properties was investigated by two complementary tests: decrease in the affinity of ouabain binding to human red blood cells and inhibition of Na⁺, K ⁺-ATPase. The results of the two methods were correlated (r = 0.76, n = 44, p < 0.01), suggesting that the same factor may be responsible for both effects. All subjects with elevated values were hypertensive or normotensive and had a family history of hypertension. Forty percent of the subjects in these two groups had high inhibition values. The elevation was significant (p < 0.01) when compared with values in normotensive subjects with no hypertensive heredity. Increased inhibition was observed in patients taking β-blocking agents; conversely, diuretics normalized the values. No correlation was found between pump inhibition and age, sex, blood pressure, levels of plasma K⁺ or Na⁺, or plasma renin activity. These data show the existence of a sodium pump inhibitor in the plasma of some subjects and point to a possible association with hypertension. They also underline the importance of genetic background and the heterogeneity of essential hypertension.