Calcium Metabolism in Rats Fed Diets Containing Various Concentrations of Magnesium

摘要

It has been shown earlier in rats that an increase in the dietary magnesium concentration causes higher rates of calcium excretion with urine. The hypothesis tested in this study was that the magnesium-induced rise in urinary calcium excretion is associated by an increase in intestinal calcium absorption and/or a lowering of calcium deposition in tibia. Female rats aged 4 weeks were fed purified diets containing magnesium concentrations of 0.02, 0.04, 0.06, 0.12 or 0.24% for a period of 6 weeks. There was no effect of dietary treatment on growth and feed intake. Dietary magnesium concentrations higher than 0.02% produced a significant increase in urinary calcium excretion. Apparent calcium absorption and tibia calcium concentrations were not affected by magnesium intake. The efficiency of apparent calcium absorption fell markedly with increasing age. It remains unknown how calcium homeostasis is attained in rats fed magnesium-rich diets.