Iron intestinal transport
This is by two main mechanisms
- Reduced, nonheme iron (Fe2+is taken up by the apical brush border membrane protein divalent metal transporter 1 (DMT1)
- Heme iron is taken up by the proximal bowel enterocyte memprane protein heme carrier protein 1(HCP1)
Some Fe2+ is retained within the cell for use or stored in ferritin. The rest is exported to the circulation by ferroportin, a membrane transporter protein. This iron is oxidized to Fe3+ and can then bind to plasma transferrin. Some heme is likely catabolized by heme oxygenase and presumably the inorganic iron so released follows the storage and export pathways above. However the heme exporter proteins, BCRP and FLVCR might export heme intact from the enterocyte into the blood.