Systemic and renal vascular responses to dietary calcium and vitamin D.

To assess the consequences of hypercalcemia on systemic and renal hemodynamics, vasoactive hormones, and water and electrolyte excretion in intact, conscious mongrel dogs, measurements in 10 dogs receiving 100 mg/kg calcium gluconate and 10,000 U/kg vitamin D daily for 2 weeks were compared with measurements made in 10 time-control dogs not receiving calcium or vitamin D. Hypercalcemia induced by dietary supplementation with calcium and vitamin D resulted in profoundly reduced glomerular filtration rate (40 vs 78 ml/min in controls; p less than 0.005), estimated renal plasma flow (145 vs 267 ml/min in controls; p less than 0.005), and renal blood flow (254 vs 441 ml/min in controls; p less than 0.005). Renal resistance was significantly increased in the hypercalcemic dogs (0.57 +/- 0.07 vs 0.28 +/- 0.01 mm Hg/ml/min; p less than 0.005). Hypercalcemia also resulted in increased fractional excretion of water (4.8 vs 1.4% in controls; p less than 0.005), sodium (1.4 vs 0.6% in controls; p less than 0.005), calcium (1.7 vs 0.7% in controls; p less than 0.01), and magnesium (10.2 vs 4.1% in controls; p less than 0.005). Systolic blood pressure (160 vs 172 mm Hg in controls; p less than 0.05) and stroke volume were lower (0.024 vs 0.036 L/beat in controls; p less than 0.005) in hypercalcemic dogs, presumably because of the diuresis, while total peripheral resistance was higher (36 vs 31 mm Hg/L/min; p less than 0.05) in controls. Magnesium levels were significantly lower in the experimental group (1.3 vs 1.7 mg/dl in controls; p less than 0.0005). Aldosterone levels, plasma renin activity, and urinary prostaglandin excretion were not significantly affected.(ABSTRACT TRUNCATED AT 250 WORDS)