The primary site for absorption of dietary iron is the duodenum. Ferrous iron (Fe2+) is taken up from the gut lumen across the apical membranes of enterocytes and released into the portal vein circulation across basolateral membranes.The human gene SLC40A1 encodes the metal transporter protein MTP1 (aka ferroportin or IREG1). This protein resides on the basolateral membrane of enterocytes and mediates ferrous iron efflux into the portal vein (Schimanski et al. 2005). MTP1 colocalizes with hephaestin (HEPH) which stablizes MTP1 and is necessary for the efflux reaction to occur (Han & Kim 2007, Chen et al. 2009). As well as the dudenum, MTP1 is also highly expressed on macrophages (where it mediates iron efflux from the breakdown of haem) and the placenta (where it may mediate the transport of iron from maternal to foetal circulation). It is also expressed in muscle and spleen.
van der Hee, RM,
ferrous iron transmembrane transporter activity of SLC40A1:HEPH:6Cu2+ [plasma membrane]