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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.
Insights
Researchers found that digestive enzymes can affect iron absorption studies in rats. Iron transport involves chelates and ferritin, with mucosal ferritin levels varying based on age and iron status.
Area of Science:
- Biochemistry
- Gastroenterology
- Cell Biology
Background:
- Ferritin is the primary intracellular iron-storage protein.
- Intestinal mucosal iron metabolism is crucial for systemic iron homeostasis.
- Previous studies have suggested a role for ferritin in intestinal iron absorption.
Purpose of the Study:
- To investigate the characteristics of rat intestinal mucosal ferritin.
- To elucidate the role of ferritin in intestinal iron absorption and transport.
- To understand the regulation of iron absorption by iron status.
Main Methods:
- Ferritin purification from rat intestinal mucosa and other tissues.
- Electrophoretic analysis of ferritin.
- Oral and parenteral administration of 59FeCl3 to rats.
- Measurement of radioactivity in mucosal cell sap and ferritin.
- Iron absorption studies in iron-deficient rats.
Main Results:
- Rat intestinal mucosal ferritin yielded low amounts and showed distinct properties compared to ferritin from other tissues, suggesting enzymatic degradation.
- Ferritin accounted for only 5-10% of mucosal iron, with a significant portion of absorbed 59Fe found in cell sap as ferritin and low-molecular-weight iron species.
- Mucosal ferritin content correlated with age and iron status, decreasing in iron deficiency.
- Iron status rapidly influenced iron transport at the serosal surface in iron-deficient rats.
Conclusions:
- Digestive enzyme activity during isolation impacts rat intestinal ferritin characteristics.
- Iron transport in the intestinal mucosa involves a rapid equilibrium between chelates and ferritin.
- Iron absorption regulation is influenced by iron status, affecting transport dynamics at the cell surface.