Intracellular Cation Activities and Concentrations in Spontaneously Hypertensive and Normotensive Rats

1. The intracellular concentrations of Na⁺, K⁺ and Ca²⁺ were measured in the erythrocytes of spontaneously hypertensive rats and normotensive Wistar rats.

2. The intracellular Na⁺ concentration in hypertensive rats was slightly elevated at 3.16 ± 0.25 compared with 2.85 ± 0.35 mmol/l (P ≈ 0.05) and intracellular Na⁺ activity was markedly increased in hypertensive rats.

3. Intracellular Ca²⁺ activity was 7519 ± 28 990 nmol/l of free water in hypertensive rats compared with 123 ± 98 in controls (P < 0.01).

4. The cytoplasm of hypertensive animals did not buffer Ca²⁺ as effectively as that of normal animals.

5. It is concluded that a decreased binding capacity of intracellular macromolecules for Na⁺ and Ca²⁺ may explain the disturbances of intracellular electrolyte composition in spontaneously hypertensive rats.