Free intracellular calcium in essential hypertension. Effects of nifedipine and captopril.

The acute effects of nifedipine (20 mg sublingually) and of captopril (12.5 mg orally) on blood pressure and on platelet intracellular free calcium were investigated in 11 and 12 patients, respectively, with essential hypertension. Platelet calcium was measured by the Quin 2 method. Application of both drugs resulted in a significant fall in blood pressure within 60 min. Platelet calcium, however, was lowered by nifedipine only. There was no correlation between blood pressure reduction and changes in platelet calcium. Platelet intracellular free calcium concentration was 99 +/- 3 nmol in 30 normotensive subjects and 109 +/- 5 nmol (+/- s.e.m.) in 26 patients with essential hypertension (P < 0.05). There was a wide overlap between the values of normotensives and hypertensives. Thus there is no positive evidence of an increased platelet intracellular free calcium concentration in a large proportion of patients with essential hypertension.