Plasma Na+-K+ ATPase inhibitory activity in normal and hypertensive subjects: relationship to intracellular electrolytes and blood pressure.

The ability of plasma extracts to inhibit Na+-K+ ATPase in vitro (P.I.A.) was tested in 20 normotensives, 10 without (F-) and 10 with (F+) familial hypertension, in 20 borderlines (BL) and in 21 essential hypertensives (EH). In these subjects we also measured intralymphocytic sodium (ILSC) and potassium (ILKC) content, P.R.A. urinary aldosterone and Na+(Na+u), and blood pressure. P.I.A. of EH, BL and F+ subjects was significantly higher than that of F-. 60% of EH and BL and 40% of F+ had P.I.A. values greater than the highest found in F-. P.I.A. was significantly related to mean blood pressure (r = 0.63), to ILSC (r = 0.56), to ILKC (r = -0.56), to ILSC/ILKC ratio (r = 0.71) and to Na+u (r = 0.39) but not to P.R.A. or aldosterone. These data demonstrate that plasma extracts from young subjects prone to hypertension may inhibit sodium pump and that this inhibitor may affect blood pressure by altering the Na+/K+ intracellular ratio.