High dietary calcium attenuates the enhanced vasoconstrictor effects of serum from salt-loaded rats

Abstract

The effect of calcium supplementation and salt loading on blood pressure, serum electrolytes, and vasoconstrictor response to serum and vascular prostaglandin synthesis were studied in Sprague Dawley rats. The mean arterial pressure of salt-loaded rats was higher (P < 0.05) than the mean arterial pressure of normal rats, salt-loaded-calcium-fed rats, or calcium-fed rats. Serum from salt-loaded rats had lower serum potassium (4.47 ± 0.39 Meq/L) and salt-loaded-calcium-fed rats (5.14 ± 0.47 Meq/L). The vasoactivity of serum from the salt-loaded rats (1116.67 ± 160.13 mg) was higher than the contraction produced by sera from normal rats (643.80 ± 37.50 mg) or from salt-loaded-calcium fed rats (562.47 ± 37.50 mg). Indomethacin did not alter the contractile response of aortae from normal rats and salt-loaded rats to noradrenaline, but it significantly enhanced the contractile response of aortae from salt-loaded-calcium-fed and calcium fed rats. The results suggest that dietary calcium may lower blood pressure by reducing the circulating levels of some plasma vasoactive factors induced by salt loading and by enhancing the synthesis of vasodilator prostaglandins.