Sodium and hypertension: effect of dietary calcium supplementation on blood pressure.
Normotensive female Wistar Kyoto rats were studied to examine the effects of replacing drinking water with highly palatable saline solution at a concentration (0.5%) close to the maximum preferred concentration in these animals. A further group of animals was offered a calcium-supplemented diet in addition to substitution of drinking water with saline. Fluid consumption in animals drinking tap water was constant at between 35-40 ml/day throughout the six-month study period. In contrast, animals drinking 0.5% saline consumed 75-85 ml/day throughout the study period, irrespective of the calcium content of the diet. Voluntary consumption of these quantities of saline was associated with the development of a moderate hypertension, measured by tail cuff plethysmography, after two months of study. However, in animals consuming calcium-supplemented diets the hypertensive response disappeared after 3 months of study. Blood pressures were validated at the conclusion of the study by direct arterial cannulation and confirmed the presence of hypertension in saline drinking animals only when diets lacked calcium supplementation. No changes in blood ionized sodium concentration were associated with saline consumption; however, blood ionized calcium was significantly reduced in animals drinking saline, but not when calcium-supplemented diet was available. These studies suggest an interaction between sodium and calcium in the genesis of sodium-dependent hypertension.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002136:Calcium, Dietary / Q000494:pharmacology*; D005260:Female; D006973:Hypertension / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
D002136:Calcium, Dietary; D012964:Sodium