EFFECTS OF CALCIUM ON ABSORPTION AND RETENTION OF LEAD

  • 1 January 1978
    • journal article
    • research article
    • Vol. 91  (3) , 366-376
Abstract
An inverse relationship between Pb retention and dietary Ca content exists but the reasons for this association were unknown. In rats the manipulation of dietary Ca had no significant effect on the absorption of Pb, but Ca-deprived animals had decreased excretion and thus increased body retention of Pb. Intraluminal Ca decreased the absorption of test doses of Pb from the small intestine in a dose-related manner. This probably occurred because the 2 metals competed for similar binding sites on intestinal mucosal proteins which were important in the absorptive process. In vivo, Pb bound to 2 heat-stable intestinal mucosal fractions which bound Ca. Although more Pb bound to the higher MW fraction and more Ca bound to the lower MW vitamin D-induced CaBP [calcium binding protein], substantial amounts of Pb and Ca were found in both fractions. The addition of Ca to test doses of Pb markedly diminished the amount of Pb bound by both fractions. Shared binding sites on absorptive proteins would explain why dietary Ca decreases Pb absorption. [Pb now contaminates virtually all foodstuffs, and a more complete understanding of not only it toxicology, but also its physiology, is important.].