Intracellular Na⁺ and Ca²⁺ Activities in Essential Hypertension

1. The intracellular Na⁺ and Ca²⁺ activity and Na⁺ concentration were measured in erythrocytes of normotensive subjects, with and without a familial disposition to hypertension, in essential hypertensive patients with and without a family history of hypertension, and in patients with secondary hypertension.

2. In normotensive subjects without a genetic trait of hypertension intracellular Na⁺ activity and concentration were 7.00 ± 1.38 mmol/l and 5.67 ± 0.95 mmol/l respectively. The intracellular Ca²⁺ activity was 4.82 ± 4.49 μmol/l. In normotensive subjects with a familial hypertensive disposition intracellular Na⁺ activity and concentration were 9.74 ± 1.43 mmol/l (P < 0.01) and 6.63 ± 0.88 mmol/l (P < 0.05). Intracellular Ca²⁺ was 9.59 ± 9.71 μmol/l (P < 0.05).

3. Essential hypertensive patients without a familial genetic trait had an elevated intracellular Na⁺ activity (8.35 ± 2.08 mmol/l, P < 0.05). Intracellular Na⁺ concentration was 6.64 ± 0.79 mmol/l (P < 0.05). The intracellular Ca²⁺ activity was markedly elevated to 25.33 ± 19.03 μmol/l (P < 0.01). The essential hypertensive patients with a familial disposition had an elevated intracellular Na⁺ activity (17.19 ± 4.37 mmol/l, P < 0.001) and Ca²⁺ activity (32.8 ± 32.51 μmol/l, P < 0.01). The intracellular Na⁺ concentration was 6.25 ± 1.23 mmol/l.

4. The results indicate that in essential hypertension intracellular Na⁺ activity is increased, particularly in patients with a familial disposition for hypertension. Intracellular Ca²⁺ is increased in essential hypertension whether or not there was a family disposition to hypertension.