Effects of high-calcium and/or high-sodium diet on basal and angiotensin II-stimulated blood pressure in the spontaneously hypertensive rat.

Direct conscious blood pressure (BP) was measured via indwelling femoral cannula to evaluate the effects of chronic diet supplements with Na, Ca or both, offered to 3-week-old weanling spontaneously hypertensive rats (SHR). Despite similar food intakes, body weights were reduced within 1-2 weeks on high-Ca diets. Blood pressure was unchanged by 5.5 weeks of diet treatments. However, irrespective of concomitant Na supplement, more prolonged treatment with the high-Ca diet completely abolished the further increase in BP between the 9th and 12th weeks of age, which was noted in the rats fed the normal or high-Na diets. Angiotensin-stimulated BP was attenuated by high-Ca diets regardless of diet Na, similar to basal readings. These weight and pressure effects of Ca were not reproduced by high-Na diet alone. For all four groups, BP was directly and significantly correlated with body weight, both at 9 and 12 weeks of age. These studies demonstrate the potential role of growth retardation in the antihypertensive action of oral Ca loading in young rats.