Hepatic proteins isolated from control kennel dogs bound small quantities of zinc and iron and the peptide fraction contained neither metal. 2. Zince loading of kennel dogs stimulated an hepatic uptake of five times more zinc and three times more iron than an equivalent copper load. The increase in metal concentration was noted in the 10,000 dalton protein. 3. Both the 12,000 and 10,000 dalton proteins isolated from kennel dogs contained more binding sites specific for zinc than for either copper or iron. All three proteins isolated from Alaskan Malamutes showed a smaller affinity for zinc than copper or iron. 4. Both copper and zinc loading stimulated an uptake of [14C]glucosamine and [3H]serine from the peptide fraction of control kennel dogs into the 10,000 dalton protein.
