ASSOCIATION OF MAGNESIUM-DEFICIENCY WITH THE BLOOD PRESSURE-LOWERING EFFECTS OF CALCIUM

The role of dietary calcium and magnesium in the development of hypertension was studied in nine groups, each consisting of nine spontaneously hypertensive rats aged 8-31 weeks. The animals were fed AIN 76A semi-purified diets varying in calcium (0.075, 0.5 and 2.5%) and magnesium (0.01, 0.05 and 0.75%) concentrations according to a 3 × 3 factorial design. Dietary calcium and systolic blood pressure were inversely related, significantly (P < 0.05) after 12 weeks. Total and ultrafilterable serum calcium concentrations were also significantly negatively correlated with blood pressure (r = −0.46; P = 0.001 and r= −0.57; P = 0.001, respectively). Repeated measures analysis of variance indicated that dietary magnesium had no effect on systolic blood pressure, and no calcium × magnesium interaction on blood pressure was observed. Signs of magnesium deficiency, calcium deposits in the kidneys, and histological lesions were observed in groups on a high-calcium diet receiving normal and low levels of magnesium. Thus a lowering of blood pressure by calcium supplementation, without concomitant magnesium supplementation, was accompanied by biochemical and histological abnormalities in this animal model. © Current Science Ltd.