Zinc Interference with Copper Absorption in Rats

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Abstract
A study was made to determine the site or sites at which zinc interferes with the intestinal absorption of copper. 64Cu was administered to all rats via ligated, in vivo, segments of duodenum, and zinc was administered either intraduodenally or intraperitoneally. High levels of zinc depressed the absorption of 64Cu when both the zinc and the 64Cu were placed directly into the isolated segment. If the 64Cu was put into the intestinal segment and the zinc was given intraperitoneally, no depression in 64Cu absorption resulted. However, the rats given intraperitoneal injections of zinc had tissue zinc concentrations that were comparable to those of rats given zinc intraduodenally. These results indicate that zinc does not depress copper absorption by first building up to critical levels in some non-intestinal tissue or tissues and, subsequently, interfering with copper absorption. Rather, the evidence indicates that the depression of copper absorption by high levels of zinc is mediated either in or on the intestine.