Mucosal block theory

Fig. 3. The mucosal block theory of iron absorption. Iron taken up by the mucosal cell is converted to ferritin when the ferritin becomes physiologically saturated with iron, no more is taken up by the cell until iron is released from ferritin and transferred to the plasma...

Some explanation of the one-way absorption of iron was afforded by the mucosal block theory in which discharge of iron into the blood stream by the mucosal cells was assumed to be controlled by the concentration of iron in the serum. Serious objections to this concept were provided by the finding of high iron absorption in untreated pernicious anemia and in pyridoxine deficiency,in which conditions serum iron is high. Uptake... 

Inasmuch as almost no iron is excreted, the mechanism controlling the levels of the iron reserves in the body must operate at the level of absorption [27, 28]. For many years the most popular theory invoked to explain the control of iron uptake was the theory of the mucosal block mechanism. The theory postulated the existence of a single, short-loop feedback mechanism within the cell of the intestinal mucosa. The absorbed iron would induce the de novo synthesis of apoferritin, and the apoferritin would then chelate iron to yield... 

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