Incorporation of iron from an oral dose into the ferritin of the duodenal mucosa and the liver of normal and iron-deficient rats.

To further characterize the role of ferritin in regulating iron absorption, uptake of an oral dose of 59Fe (0.2 mg Fe/kg body wt.) into duodenal and hepatic ferritin of control and iron-deficient (ID) rats was studied. Retention and uptake of 59Fe from Fe(II)-sulfate, Fe(III)-chloride, or Fe(III)-polymaltose were measured up to 28 h after dosing. Ferritin was determined by radioimmunoassay (RIA) and 59Fe ferritin-iron by gel electrophoresis. Retention and liver content of 59Fe was higher in ID rats than in controls. The mucosa of ID rats, however, retained only one third of the amount of 59Fe retained by the mucosa of controls. The mucosal and hepatic ferritin levels were lower in ID rats than in controls. The percentage of orally administered 59Fe found in the liver ferritin was therefore higher in control than in ID rats. However, when expressed as per unit of ferritin, iron uptake was eight times higher in ID rats. In contrast, mucosa ferritin of ID rats contained one-third of 59Fe per unit of ferritin than that of controls. Assuming no change in the mechanism of iron uptake into ferritin of control and ID rats, the differential uptake of oral iron into mucosa and liver ferritin indicates either a different compartmentation of the tissue ferritin or differences in the iron transport processes, but mucosal ferritin does not withdraw iron from intestinal absorption.