Gastrointestinal absorption of lead (203Pb) in chicks: influence of lead, calcium, and age.

The present study was designed to investigate, in more detail, the mechanism of lead transport by the gastrointestinal tract and particularly the similarities or dissimilarities between lead and calcium in this process. The absorption of these metals was determined in 3-week-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 microCi 203Pb (and/or 0.1 microCi 47Ca), 0.01 mM lead acetate (and/or 1 mM CaCl2) in 0.5 ml of 0.15 M NaCl, pH 6.5. It was shown that lead is rapidly taken up by the intestinal tissue, and only slowly transferred into the circulation whereas calcium, also accumulated rapidly by the tissue, is rapidly released from the tissue in the serosal direction. The absorption processes of these cations show similar responses to various experimental conditions (low calcium intake, age of the animal, pH of the dosing solution). However, increasing luminal stable lead concentration from 0.01 to 1 mM Pb, significantly reduced the percentage of radiolead absorbed, but did not inhibit the absorption of radiocalcium, Also, luminal Ca (0-25 mM) did not significantly affect the absorption of 203Pb. These data imply that, in spite of the similarities in the response of the lead and calcium absorptive processes to various treatments, there is no direct interaction between these cations in the intestine of the chick.