Copper absorption in sheep.

Female sheep were used to determine the regions of the gastrointestinal tract able to absorb Cu. Copper was absorbed from the abomasum, small intestine and colon, but not from the rumen-reticulum or caecum. In vitro studies indicated that Cu uptake was linearly related to the Cu concentration. Copper complexed to histidine, lysine or glutamine was absorbed in a similar manner to ionic Cu and at a similar rate. In vitro Cu uptake was not affected by ouabain, rotenone, oligomycin, 2,4-dinitrophenol fluoride or zinc. The in vitro data show that lumen-to-mucosal cell Cu transfer has kinetics reflecting simple diffusion rather than a saturable, energy-dependent process.