[Results of the evaluation of platelet sodium-proton exchange in the young hypertensive subject]. 
In order to assess the relationships between increased cellular sodium-proton (Na+/H+) exchange and cardiovascular abnormalities in essential hypertension (EH), 21 young subjects as part of an ongoing longitudinal study were tested for the platelets Na+/H+ exchange using the amiloride sensitive sodium dependent component of platelet volume change under cytoplasmic acidification induced by a sodium propionate medium; cell volumes were determined by electronic cell sizing (Livne et al.,  Lancet 1987; i: 533-6).  24 normal subjects with normotension and without familial history of hypertension were taken as controls.  Data of ambulatory blood pressure recording (ABPR) defined 2 groups according to the presence of normotension (group I, n = 10), or of hypertension (group II, n = 11): established (n = 2) or borderline (n = 9) hypertension.  Hypertensive subjects (group II) had increased values of Na+/H+ exchange (k coefficient, mean (SEM): 0.287 (0.07) vs 0.228 (0.05) in control group (p less than 0.01).  Na+/H+ rates were significantly related to ABPR data (r = 0.46, p less than 0.02 with diastolic charge during ABPR), but not to left ventricular mass index in g/m2 by echocardiography.  Increased rates of platelets Na+/H+ exchange which were related to diastolic blood pressure levels by ABPR, and perhaps to the level of peripheric vascular resistances, may play a significant role in the development of EH in the early stages.