Intracellular sodium and calcium in essential hypertension.

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.