Effect of Graded Levels of Cadmium on Tissue Uptake of 65Zn by the Chick Over Time

Publisher Website
Google Scholar
Abstract
To ascertain if part of the interference of dietary cadmium with the utilization of dietary zinc might be due in part to competition for sites on a blood transport system, and to detect other early interference, chicks were fed graded levels of cadmium with each of three levels of a single dose of 65Zn. Uptake by the blood, liver and tibiae was measured over a 24-hour period. Interference with uptake of 3 µg of 65Zn was not found when zero, 5, 10 or 50 ions of Cd (mole equivalents) were included in the dosage. When a basal dose of 18 or 27 µg of 65Zn was fed, 5 or 10 molEq of cadmium caused a marked decrease in absorption of 65Zn. The difference in blood levels persisted over 24 hours, suggesting that cadmium was occupying some of the blood-binding sites. The 65Zn accumulated in the liver of the chicks fed cadmium so that uptake did not differ from the basal group from 8 to 24 hours. The increase in liver uptake was not reflected in uptake by the tibiae, the latter being significantly lower than the basal group. It is postulated that cadmium interferes with the absorption of zinc through occupation of some of the binding sites of a transport system in the blood; further interference with utilization of the absorbed zinc occurs at a more fundamental level. It is suggested that the effect of dietary cadmium on dietary zinc will depend on the absolute amounts of each, the proportions of one to the other, and the length of the feeding period.