Figure 2.

Mechanism of iron transfer across the placenta. The syncytiotrophoblast takes up iron-transferrin from maternal circulation via the transferrin receptors (TfR) cycle. After the holo-Tf/TfR complex is endocytosed, and iron is released from the complex in the acidifed endosome, iron is transported into the cytosol likely by the divalent metal transporter-1 (DMT-1). Iron is exported from the basolateral side of the synctiotrophoblast into fetal circulation by ferroportin (Ireg1). A ferroxidase (possibly zyklopen) oxidizes iron so it can be loaded onto fetal transferrin [28]. (with permission to publish photo from Nutrition Reviews).