The regulation of Na-K cotransport system and essential hypertension

We have determined in human red cells the equilibrium position between outward and inward furosemide-sensitive (FS) Na-K cotransport, by measurements of unidirectional 22Na and 42K influx and efflux. At physiological Na and K concentrations, the system performs net Na and K extrusion. In vascular endothelial cells, the Na-K cotransport system performs net Na influx and is stimulated by vasoactive peptides (bradykinin and vasopressin). Measurements of red cell Na-K cotransport performed by other investigators are discussed. Measurements of outward cotransport as a function of internal Na (nystatin loading) indicate that a subset of hypertensive subjects has higher K0.5 for internal Na to promote FS Na efflux.