The Role of the Intestinal Mucosa in Iron Absorption*

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Abstract
A study was made of the chemical form of iron within rat duodenal cells during its absorption from the intestinal lumen. One fraction consisted of iron in transit across the mucosa during the early phase of rapid absorption. The nature of this fraction was not established, although several of its properties were defined. The remainder of the iron taken up into the cell was temporarily stored in the form of ferritin. If required, this iron was probably available for slow release into the plasma, but under certain circumstances was held within the cell. With exfoliation of the mucosal epithelium the trappedferritin iron was lost. The deviation of iron into ferrit in may therefore represent a mechanism for preventing excessive absorption. Some evidence was obtained to suggest that the proportion of absorbed iron which is trapped in this way by the individual mucosal cell is determined before the cell reaches its functional position on the intestinal villus. One factor modifying mucosal behaviour is probably the iron concentration in the environment during cellular development in the intestinal crypts.