Correlation of increased serum calcium with elevated blood pressure and vascular resistance during calcium infusion in normotensive man.

The effects of intravenous calcium infusion on blood pressure (BP) and total peripheral vascular resistance (TPR) were investigated in seven normotensives at rates of 3.75, 7.5 and 15.0 mg/kg per h for 1 h. The infusions increased serum calcium levels, with significant elevations of BP and TPR, but had no effect on cardiac output, indicating that the TPR elevation induced the BP rise. The increase in serum calcium was correlated with elevations of systolic, diastolic and mean BP and TPR (r = 0.74, 0.78, 0.77 and 0.82, respectively; P less than 0.001); greater increases in serum calcium resulted in greater elevations of TPR and BP. The serum calcium increase was also associated with reductions in plasma parathyroid hormone and renin activity, and an increase in plasma aldosterone, which might have contributed to the rise in BP. Our results suggest that an increased serum calcium level led to calcium influx into arterial smooth muscle, which increases cytosolic calcium, induces muscle contraction, and thereby produces arterial vasoconstriction, leading to elevations of TPR and BP.