Influence of a calcium-enriched diet on salt-induced hypertension in rats.

Addition of dietary calcium exerts antihypertensive effects in spontaneously hypertensive rats (SHR), which can be intensified by a parallel increase of sodium in the diet. It was of interest to what extent calcium addition to a high salt diet might modify salt-dependent hypertension in salt-sensitive Dahl rats (S/JR). Groups of six S/JR and seven salt-resistant Dahl rats (R/JR) received, when 4 weeks old, diets containing differing sodium and calcium concentrations. A further group received a calcium-enriched diet supplemented with the calcium antagonist nitrendipine. A higher calcium content in the diet did not change the effects resulting from an 8% NaCl diet, with regard to heart weight and laboratory parameters. Salt-sensitive Dahl rats on a calcium-enriched NaCl diet had a more rapid development of hypertension than S/JR on a normal calcium/high salt diet or S/JR on a calcium-enriched diet supplemented with nitrendipine. Salt-resistant Dahl rats did not differ significantly with regard to blood pressure development on any diet. In contrast to the effect in SHR, dietary calcium has therefore no antihypertensive effect on salt-induced hypertension. A moderate increase in the calcium content of the diet does not alter blood pressure lowering effects of calcium antagonists.