Effect of increased dietary calcium on the development of reduced renal mass saline hypertension in rats.

Abstract

A diet fortified with calcium carbonate has been reported to reduce blood pressure in low-renin and salt-sensitive hypertensive patients. We have therefore examined the effect of increased dietary calcium on the development of reduced renal mass-saline hypertension in rats, a classical, low-renin, volume, and sodium-dependent model of hypertension. Rats with 70-75% reduction in renal mass were divided into experimental and control groups. The experimental rats were fed a sodium-free diet supplemented with calcium carbonate (2.0% calcium) and drank 1% saline for 5 weeks. Control rats consumed the salt-free diet and drank 1% saline for the same period. In control rats, as previously observed, blood pressure progressive increased from a control value of 120.0 +/- 1.2 to 174.2 +/- 1.2 mm Hg by the fifth week. In contrast, in the calcium-supplemented rats the development of hypertension was significantly attenuated; the blood pressure only increased from 117.0 +/- 1.2 to 134.0 +/- 3.8 mm Hg by the fifth week. This was associated with a 30% decrease in saline intake by the fifth week, with proportionate decreases in urine volume and sodium excretion but not potassium excretion. Urinary magnesium excretion increased. No such changes were seen in control rats. At the end of the treatment period, plasma levels of sodium, potassium, calcium, creatinine, BUN, and protein were not different, but plasma chloride and magnesium were lower in experimental rats; vascular smooth muscle cell membrane potentials were also not different. These data show that dietary calcium carbonate can attenuate the development of reduced renal mass-saline hypertension in the rat, possibly in part by altering sodium and water intake.

High dietary calcium decreases blood pressure in normotensive rats

“…The rats of group D fed a highcalcium diet for 30 days had significantly (P<0.05) lower systolic and diastolic blood pressures than the other groups. These results are consistent with studies showing supplemental calcium to be associated with a reduction of arterial blood pressure in both normotensive and hypertensive animals (17)(18)(19). Despite accumulating evidence, the mechanisms by which calcium lowers blood pressure are still unknown.…”

Effects of high calcium diet on arterial smooth muscle function and electrolyte balance in mineralocorticoid‐salt hypertensive rats

“…The present study shows a marked antihypertensive effect of increased dietary calcium in one-kidney DOC-NaCl hyperten-a 954 P. ARVOLA et al (Resnick et al, 1986;Yang et al, 1989;Pamnani et al, 1990), whereas in genetic hypertension the effect is usually only moderate (Ayachi, 1979;Porsti, 1992;Porsti et al, 1992). This suggests that the mechanisms of action of oral calcium loading may particularly involve the correction of those abnormalities characteristic of sodium-volume-dependent hypertension (e.g.…”

Dietary calcium and blood pressure in experimental models of hypertension. A review.

“…• References 54,91,119,131,137,149,156,159,173,190,191,[286][287][288] pressure. According to this hypothesis, calcium supplementation increases available calcium, prevents the fall in ionized calcium that provokes the increase in calcium-regulating hormones, and reverses the salt-induced hypertension.…”