RADIOACTIVE IRON ABSORPTION BY GASTRO-INTESTINAL TRACT : INFLUENCE OF ANEMIA, ANOXIA, AND ANTECEDENT FEEDING...

Area of Science:

• Gastroenterology and Hematology
• Nutritional Physiology
• Cellular Metabolism

Background:

• Iron absorption is regulated by the gastro-intestinal mucosal epithelium.
• Normal iron absorption is low but increases significantly with chronic anemia due to blood loss.
• Previous studies indicate iron absorption differences between normal and anemic states.

Purpose of the Study:

• To investigate the time course and factors influencing iron absorption in response to anemia.
• To examine the effect of acute anoxemia and prior iron intake on iron absorption.
• To understand the role of gastro-intestinal mucosal epithelium in regulating iron uptake.

Main Methods:

• Studies conducted on dogs and observations in humans.
• Induction of chronic anemia via blood loss and acute anoxemia.
• Administration of radio-iron orally and intravenously, with varying pre-administration iron doses and meal conditions.
• Analysis of plasma radio-iron concentration curves and distribution in tissues.

Main Results:

• Chronic anemia increases iron absorption 5-15 times normal within 7 days, even with rising hematocrit.
• Acute anoxemia does not significantly enhance iron absorption.
• Oral iron administration 1-6 hours prior to radio-iron induces a 'mucosa block', reducing uptake.
• Intravenous iron does not inhibit subsequent oral radio-iron absorption.
• Plasma iron absorption peaks vary based on stomach contents and emptying time.
• Specific organs like spleen, heart, and marrow show higher radio-iron concentration.

Conclusions:

• Iron absorption is dynamically regulated by the gastro-intestinal mucosa, influenced by the body's iron status.
• 'Physiological saturation' of the mucosa explains iron uptake regulation, with desaturation taking days and saturation occurring rapidly.
• These rapid mucosal changes are linked to cellular protein metabolism.