The Gastrointestinal Tract and Iron Absorption

1. Using Fe⁵⁹ and whole body counting, various aspects of gastrointestinal absorption of iron salts were studied in normal, iron-loaded, and iron-deficient rats.

2. Following a single intragastric dose of iron, peak small intestinal uptake was observed by 30 to 60 minutes with subsequent gradual loss over 24-hour period.

3. Iron absorption showed two phases, an initial period of rapid absorption lasting up to 2 hours during which 60 to 80 per cent of total absorption into carcass took place. The remainder took place at a slow rate over the subsequent 12 to 20 hours.

4. Depending on the relationship between body iron stores and dose of administered iron, the intestine may take up more iron than is ultimately transferred to plasma. A variable amount of this iron is lost when the epithelial cell is sloughed into the gastrointestinal lumen.

5. Regulation of iron absorption appears to involve two steps, mucosal uptake and transfer to the blood.