Process of carbonyl iron absorption from the rat duodenal mucosa

The process of carbonyl iron absorption from rat duodenal mucosa was investigated histologically with Perls' iron staining and immunostaining for ferritin and transferrin. The change in iron and ferritin distribution in the liver after oral administration of carbonyl iron was also studied. After oral administration of carbonyl iron (100 mg iron/kg body weight), stainable iron appeared not only in the duodenal lumina but also in the epithelial cell cytoplasm, intercellular spaces of epithelial cells and subepithelial stroma. Some of the stainable iron in the epithelial and their intercellular spaces was in the form of fine granules smaller than carbonyl iron particles. Mucosal ferritin increased after administration of carbonyl iron but its distribution was different from that of stainable iron. The amount and the distribution of transferrin in the duodenal mucosa were not changed after carbonyl iron administration. These observations suggested that some carbonyl iron was absorbed without the participation of ferritin and transferrin. In the liver, fine granular stainable iron appeared in the peripheral zones of the hepatic lobules around the portal vein, and liver ferritin increased after oral administration of carbonyl iron. Increased liver ferritin was detected in some of the perisinusoidal cytoplasm of hepatocytes.