Evolution of Mg deficiency in rats.

We performed weekly analyses of the evolution of the bioavailability of the Mg cation over a period of 70 days in adult rats fed an Mg-deficient (0.02%) diet. The results generally showed an increase in digestive utilization (% absorption) and a decrease in Mg balance during the experimental period. The parameters most sensitive to Mg deficiency were increase in body weight and blood concentration of Mg (mg/100 ml), which had declined significantly after 7 days (p < 0.05). Significant declines in plasma (p < 0.02) and muscle Mg (p < 0.01) were not apparent until after 35 days. Magnesium content in bone decreased from day 49 onward (p < 0.05), whereas renal Mg concentration tended to rise slightly during the last 2 weeks of study. No change was found in brain Mg concentration.