Increased platelet Na+-H+ exchange rates in essential hypertension: application of a novel test.

Enhanced sodium-proton exchange may play a role in the pathogenesis of hypertension. Na+-H+ exchange was measured indirectly in platelets as the rate of amiloride-sensitive and sodium-dependent volume gain of cells suspended in sodium-propionate; the cytoplasmic acidification induced by the permeant propionic acid activated the exchanger and the volume changes coupled to Na+ uptake were measured by cell sizing with a Coulter counter and 'Channelyzer'. The test was rapid, simple, and reproducible. 20 normotensives; 8 normotensives with a family history of hypertension; 15 patients with essential hypertension receiving medication; and 7 hypertensives who had not received any antihypertensive drugs were studied. The exchange rate constants of these groups were (mean [SE] in s-1 X 10(-3)) 13.1 (0.6); 15.5 (0.7); 18.4 (0.9); and 25.6 (2.8), respectively. The differences between hypertensives and normotensives were significant. Measurement of sodium-proton exchange in platelets may help to clarify the pathogenesis of hypertension.