Intestinal uptake and retention of copper in the suckling rat, Rattus rattus--IV. Mechanisms of intestinal copper accumulation.

Copper-67, administered either parenterally or via the maternal milk, accumulates principally in the intestine and liver of the 6-day-old pup. Most of the 67Cu in the soluble fraction of the intestine is associated with the heterogeneous Cu-complex, which is located predominantly in the ileum. The rates of uptake and loss of 67Cu in the liver and intestine indicate that enterohepatic circulation of Cu in the neonate is appreciable. Whilst the concentration of Cu in the bile of the 13-day-old pup is high (16-fold greater than that in the adult male rat), translocation of Cu from both the liver and duodenum to the ileum probably occurs via the blood, rather than by the reabsorption of biliary Cu. Although the Cu-complex normally seems to be retained within the distal intestine until the enterocytes are desquamated, Cu in this form is utilized when the Cu-intake of the neonate is restricted.