Inherited defect in a Na⁺, K⁺ -co-transport system in erythrocytes from essential hypertensive patients

Abstract

The Na⁺ and K⁺ electrochemical gradients across cell membranes are believed to be maintained by the action of a Na⁺, K⁺-pump^1–3. In human erythrocytes this pump exchanges internal Na⁺ for external K⁺ in approximately a 1.5 ratio^4,5. Thus, when Na⁺-loaded/K⁺-depleted erythrocytes are incubated in physiological conditions they tend to recover their original low Na⁺/high K⁺ content. Surprisingly, in erythrocytes from healthy donors the net Na⁺ extrusion/K⁺ influx ratio exceeds the 1.5 ratio predicted for Na⁺, K⁺-pump-mediated fluxes whereas it is similar to this value in erythrocytes from essential hypertensive patients and some of their descendants⁶. We now report that this difference is due to the presence of a Na⁺, K⁺-co-transport system in normal erythrocytes which extrudes both internal Na⁺ and K⁺ and is functionally deficient in erythrocytes of essential hypertensive patients and some of their descendants. No difference in passive Na⁺ permeability could be detected between normotensive and hypertensive subjects.