Altered Calcium and Sodium Metabolism in Red Blood Cells of Hypertensive Man: Assessment by Ion-selective Electrodes

Abstract

Free intracellular calcium [Ca²⁺]_i, sodium [Na⁺]_i and potassium [K⁺]_i were assessed in freeze-thawed human red blood cells (RBC) by ion-selective electrodes.

After metabolic depletion by 30 mM 2-desoxy-glucose, [Ca²+]_i increased faster and to significantly higher values in RBC from 16 patients with mild to moderate essential hypertension (mean diastolic blood pressure 111 ±10 mmHg) than in the RBC of 24 normotensives. The rate of [Ca²⁺]_i increase was 7.0 ± 3.6 versus 3.7 ± 4.0 μmol/h/l cells (P<0.01) for the first 24 h and 8.1 ±4.8 versus 6.4 ± 3.5 μmol/h/l cells for the following 24 h. [Na⁺]_i before and after 24 h incubation was significantly higher in hypertensives, whereas basal [Ca²⁺]_i and [K⁺]_i before and after incubation were the same in both groups. After Ca loading by ionophore A 23187, the maximum rate of [Ca²⁺]_i extrusion was not significantly lower in intact RBC from hypertensives than in those from normotensives (59.5 ±7.8 versus 87.9 ±18.1 μmol/min/l cells).

These results indicate disturbances in RBC Ca metabolism similar to those observed earlier for Na and K. If generalized, the defect could lead to raised [Ca²⁺]_i in smooth muscle and sympathetic nerve tissue, thus causing increased vascular tone and probably catecholamine release with subsequent arterial hypertension.