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Cells employ specialized proteins to handle and store iron while minimizing oxidative stress. Absorption of dietary iron is regulated by enterocytes, which change their rate of absorption depending on total body iron stores.

Some cells, such as reticuloendothelial macrophages and hepatocytes, are specialized to store large quantities of iron, and act to maintain a reserve that can be mobilized when needed to provide functional iron to red blood cells, erythrocytes, and parenchymal cells.

Cellular iron uptake and storage mechanisms

Once it is transported to cells by transferrin, iron enters the cell by binding to transferrin receptors on the cell membrane, which are engulfed through endocytosis. Inside the endosome, iron is converted into hemosiderin, which can be released into the cytosol by a process of acidification. The transferrin receptors and apotransferrin (transferrin unbound to iron) are recycled back to the cell surface. Triggered by the neutral pH of the blood, the receptor complex releases apotransferrin. The receptor is now available to bind to another transferrin molecule.

How enterocytes absorb dietary iron

How hepatocytes store plasma-borne iron