EFFECT OF DIETARY MAGNESIUM LEVEL ON NEPHROCALCINOSIS AND GROWTH IN RATS

We studied the extent of kidney calcification by varying dietary level s of Mg, based on pathological examinations and calcium (Ca) and magne sium (Mg) balance tests. AIN-76 diets containing varying levels of Mg- 0.3 (-M), 1.3 (1/20M), 2.4 (1/10M), 9.2 (1/5M), 19 (control), 38 (2M), 102 (5M), and 187 (10M) mmol/kg diet-were fed to 3-week-old male Fisc her-344 rats for 14 d. Although the magnitude of abnormality was highe st in kidney of rats fed the -M diet, the damage was normalized as the dietary level of Mg increased, with increasing serum Mg concentration and urinary excretion of ME. We found almost no deposition of Ca in r ats fed the 10M diet. The mechanism by which the high dietary Mg induc es these effects most likely involves a competition between Mg and Ca for reabsorption in proximal and/or distal tubules, since these diets increased the urinary excretion of Ca. However, these high Mg diets de creased food intake and body weight gain compared with the control die t, although these indices were not decreased in rats fed the 2M diet. The results suggest that a dietary magnesium level approximately twice the normal level effectively reduces kidney calcification while maint aining normal growth in rats.