Platelet sodium-proton exchange is increased in essential hypertension

Transmembrane sodium-hydrogen (Na+-H+) exchange was measured indirectly in human platelets as the amiloride-sensitive change in volume during incubation in isosmotic sodium propionate. After first establishing the reproducibility of the assay, we measured propionate-activated volume increases in platelets from 24 male essential hypertensive patients and 20 male normotensives. For the entire group, platelet Na+-H+ exchange was significantly (P less than 0.006) higher in hypertensives compared with normotensives. Unlike red blood cell (RDC) cation transport markers of hypertension, platelet Na+-H+ exchange was elevated in both black and white hypertensives. Na+-H+ exchange was significantly positively correlated with diastolic blood pressure and did not correlate significantly with age, body weight or body mass index. In addition, platelet Na+-H+ exchange did not correlate significantly with red blood cell lithium-sodium countertransport activity. Platelet Na+-H+ exchange deserves further study as a marker for pathophysiological abnormalities in human hypertension.