Inhibitory Effect of High Dietary Zinc on Copper Absorption in Rats

High dietary zinc resulted in the lowering of growth, hemoglobin concentration, ceruloplasmin activity and copper concentration in liver, kidney and serum with a marked increase in the concentration of zinc in these tissues. The preliminary experiments were made to determine the sites at which zinc interferes with copper metabolism. When copper was administered to the zinc-fed rats either orally or intraperitoneally, the depression in copper uptake into liver was clearly observed in the former case. Moreover, copper uptake into liver was depressed even when both copper and zinc were administered orally to the normal rats. By the short-period experiments using 64Cu, it was also shown that zinc interferes with the absorption and utilization of copper. These results indicate that the interference of copper metabolism by zinc feeding is mainly due to the inhibition of copper absorption at the intestinal level.