Abstract
The mode of copper absorption from the gastrointestinal tract of chicks has been investigated. Studies with 64Cu indicated that copper absorption was greater from the duodenum than from the proventriculus. No absorption of copper was observed from the ventriculus. Copper-64 present in the duodenal mucosa was found to be firmly and specifically attached to protein with a molecular weight of approximately 10,000. Zinc and cadmium, inhibitors of copper absorption, appear to act as copper antagonists by binding to, and displacing copper from, the 10,000 molecular weight duodenal protein.