Intracellular
sodium and
calcium activities were measured by
ion-selective electrodes in red blood cells of primary hypertensives and of normotensives with and without a familial disposition to
hypertension. Intraerythrocytic
sodium activity was markedly elevated in patients and normotensives with a familial disposition to
hypertension (15.16 +/- 2.35 mmol/l in hypertensives and 9.74 +/- 1.43 mmol/l in normotensives, respectively, mean value +/- SD) as compared to the corresponding group without such a history (8.35 +/- 2.08 mmol/l in hypertensives and 7.00 +/- 1.38 mmol/l in normotensives). Mean intraerythrocytic
calcium activity showed the highest values in patients with
hypertension (32.8 +/- 32.5 mumol/l in patients with and 25.3 +/- 19.0 mumol/l in those without a familial disposition to
hypertension), whereas in normotensives mean
calcium activity was much lower (9.6 +/- 9.7 and 4.8 +/- 4.5 mumol/l, respectively). Our results document that a disturbed intraerythrocytic
sodium metabolism is limited to patients with
essential hypertension and a familial disposition to
hypertension and, to a lesser extent, to normotensives showing a familial disposition to
hypertension. Thus, a genetically determined alteration in intracellular
sodium can be assumed. Furthermore, the observation of an enhanced intraerythrocytic
calcium in some essential hypertensives with and without a familial disposition suggests additional factors, other than
sodium, responsible for the disturbed intracellular
calcium balance in these patients.