The effects of high dietary calcium on salt-induced hypertension in rats

The effects of dietary salt-loading and concurrent administration of dietary calcium on water and electrolyte excretion in Sprague-Dawley rats have been studied. The total salt consumed by salt-loaded rats was significantly higher than that of control rats (P < 0.05). The total salt consumed by salt-loaded calcium fed rats was also higher (P < 0.05) than that of control rats but it was slightly lower (P < 0.05) than the consumption by the salt-loaded. Rats fed only high calcium diet had the least salt consumption. The total water intake was also highest (P < 0.05) in the salt-loaded rats when compared with either control rats, salt-loaded-calcium-fed rats or calcium-fed rats. Urinary water excretion was highest (P < 0.05) in salt-loaded-calcium-fed rats followed by salt-loaded rats and calcium-fed rats while the control rats had the least. Similarly, the sodium excretion was highest in salt-loaded-calcium-fed rats followed by salt-loaded rats and calcium-fed rats and control rats respectively. Potassium excretion was highest in salt-loaded-calcium-fed rats followed by salt-loaded rats and calcium-fed rats while the control rats had the least excretion of potassium. Serum sodium concentrations were identical in all the groups although in salt-loaded rats and salt-loaded-calcium-fed rats the values were slightly higher than those of controls. However, serum potassium concentration was lowest in salt-loaded rats and calcium-fed rats while the values for salt-loaded-calcium-fed rats was not significantly different from that of control. The results of this study suggest that increase in dietary calcium intake reduces the increase in blood pressure resulting from salt-loading and this is accompanied by an increase in water and sodium excretion.