Hypertensive effects of calcium infusion in subjects with normotension and hypertension.

The hemodynamic effects of acute hypercalcemia induced by calcium infusion, 7.5 mg/kg per h for 1 h, were investigated in normotensive and hypertensive subjects, aged 43-83 years, in the absence and presence of the calcium antagonist verapamil. Calcium infusion raised blood pressure from 125 +/- 14/62 +/- 6 to 143 +/- 13/69 +/- 7 mmHg (mean +/- s.d.) and from 173 +/- 15/81 +/- 6 to 202 +/- 23/92 +/- 9 mmHg with an increase in concentration of serum calcium from 2.2 +/- 0.1 to 3.2 +/- 0.2 mmol/l and from 2.2 +/- 0.1 to 3.2 +/- 0.1 mmol/l in normotensives (n = 20) and hypertensives (n = 12), respectively. In hemodynamic studies, the calcium infusion significantly raised blood pressure and total peripheral vascular resistance and decreased heart rate with no change of cardiac output, in normotensives (n = 8) and hypertensives (n = 8). The absolute increases in both blood pressure and vascular resistance were significantly higher in hypertensives than in normotensives, but the per cent increases were not significantly different in both groups. The per cent increases in blood pressure and vascular resistance were negatively correlated with increasing age. The infusion of verapamil at the rate of 0.15 mg/kg per h inhibited the increases in both blood pressure and vascular resistance during the calcium infusion in normotensives (n = 6) and hypertensives (n = 6). In conclusion, the calcium infusion raised blood pressure because of elevated vascular resistance, and the effects of calcium on blood pressure were inhibited by the calcium antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)