Influence of Ca and Mg on the uptake and deposition of Pb and Cd in mice.

The influence of high but not extreme concentrations of Ca and Mg (25 mumol/ml) on the apparent absorption and retention of 203Pb and 115mCd from water was investigated in mice. Ca reduced the absorption of Pb from an intubated solution by 62% and the absorption of Cd by 22%, but these effects were not significant. Mg showed no effect on Pb and Cd absorption. The retention of ip-injected Pb and Cd was not influenced by addition of Ca or Mg to the drinking water. Feeding of a Ca-deprived diet for 2 weeks prior to dosage stimulated the absorption of Pb from water by more than 100% (p less than 0.01) and the absorption of Cd from water by 17% (p less than 0.05). Feeding of a Ca-supplemented diet did not influence the absorption of Pb or Cd, but fecal Cd excretion seemed to be reduced. Feeding of Mg-deprived or Mg-supplemented diets did not show any effect on Pb and Cd metabolism. These results give supporting evidence that in soft water regions the uptake of Pb from the drinking water could be increased because of the absence of Ca in the drinking water, particularly when dietary Ca intake is low. This relationship between drinking water hardness and absorption of Pb could be important in view of general public health.