Effect of vitamin D and low dietary calcium on lead uptake and retention in rats

The effects of cholecalciferol (formerly vitamin D-3) supplementation and alterations in dietary calcium levels on intestinal 210Pb absorption and tissue uptake were studied in weanling female Sprague-Dawley rats. Rats were placed in one of three groups: 1) normal dietary calcium with normal cholecalciferol; 2) low dietary calcium with normal cholecalciferol; or 3) normal dietary calcium with cholecalciferol supplementation. Blood 210Pb levels were determined at 3, 6, 12 and 24 hours following the administration of either an oral or an IP dose of 210Pb. Femur and kidney 210Pb activities were subsequently determined for all animals 24 hours after the administration of 210Pb. Cholecalciferol supplementation resulted in increased net intestinal absorption of 210Pb with uptake into femurs and kidneys. The effect of cholecalciferol to increase tissue uptake of 210Pb was shown to be independent of the effect of cholecalciferol on the gastrointestinal absorption of lead. A lowering of dietary calcium was shown to increase lead absorption with uptake into femurs; however, this increased tissue uptake of lead was shown to be dependent upon increased intestinal lead absorption and was not a direct effect of the low calcium diet.