Ferritin and intestinal iron absorption: pancreatic enzymes and free iron

Abstract

Rat intestinal mucosa gave low yields of ferritin purified by standard procedures. The resulting ferritin had less protein relative to iron and migrated faster electrophoretically than ferritin from other rat tissues. Pancreatic duct ligation reduced these differences, suggesting digestive enzyme attack during ferritin isolation. Even in ligated rats, ferritin accounted for only 5-10% of mucosal iron. However, shortly after giving 59FeCl3 orally, 50% of mucosal radioactivity occurred in cell sap, about equally distributed between ferritin and low-molecular-weight (chelated?) iron. No other cell sap components were 59Fe labeled. Iron may thus be transported as a chelate with which ferritin is in rapid equilibrium. Mucosal ferritin content increased with age and iron treatment and decreased with iron deficiency. The iron-deficient rats showed accelerated 59Fe uptake into blood with little mucosal retention. One day after administering parenteral iron to deficient rats, 59Fe transfer to blood became retarded but 59Fe now accumulated excessively in the mucosa, suggesting that iron status affects transport more rapidly at the serosal than at the mucosal cell surface. A scheme for control of iron absorption is presented.