The hemodynamic effect of dietary calcium supplementation on rat renovascular hypertension.

Mechanisms which could be responsible for the hypotensive effects of increasing calcium intake from 1.2 to 2.5% of diet were examined in two kidney, one clip renovascular hypertension (2K, 1C RHV) in male Sprague-Dawley rats. Plasma renin activity was elevated similarly in NCA and HCA rats. No evidence for volume or phosphate depletion was found in HCA animals. Cardiac output was not different. Decreased sensitivity was demonstrated to moderate doses of norepinephrine in HCA rats, while vascular reactivity to exogenously administered angiotensin II over the range of doses used was not different between diets. The antihypertensive effect of supplemental calcium was associated with a 39% reduction in systemic vascular resistance. Therefore, dietary calcium supplementation lowers blood pressure in 2-K, 1C RVH primarily due to a systemic vasodilatation and reduced vascular reactivity to moderate doses of norepinephrine.