GASTROINTESTINAL ABSORPTION OF LEAD (PB-203) IN CHICKS - INFLUENCE OF LEAD, CALCIUM, AND AGE

The mechanism of Pb transport by the gastrointestinal tract and the similarities or dissimilarities between Pb and Ca in this process were studied. The absorption of these metals was determined in 3-wk-old white Leghorn cockerels, raised on a commercial diet or special diets, using an in vivo ligated loop procedure. The dose administered into the loop usually contained 0.5 .mu.Ci 203Pb (and/or 0.1 .mu.Ci 47Ca), 0.01 mM lead acetate (and/or 1 mM CaCl2) in 0.5 ml 0.15 M NaCl, pH 6.5. Pb was rapidly taken up by the intestinal tissue and only slowly transferred into the circulation; Ca also accumulated rapidly by the tissue, was rapidly released from the tissue in the serosal direction. The absorption processes of these cations showed similar responses to various experimental conditions (low Ca intake, animal age, pH of the dosing solution). Increasing luminal stable Pb concentration from 0.01 to 1 mM Pb significantly reduced the percentage of 203Pb absorbed but did not inhibit the absorption of 47Ca Luminal Ca (0-25 mM) did not significantly affect the absorption of 203Pb. In spite of the similarities in the response of Pb and Ca absorptive processes to various treatments, there was no direct interaction between these cations in the intestine of the chick.