Localization and Kinetics of the Transferrin-Dependent Iron Transport Machinery in the Mouse Placenta

The placenta transports iron to the fetus to support growth and development. Mice are commonly used to study placental iron transport. The subcellular locations of transferrin receptor and ferroportin 1 in iron-transporting cells in the mouse placenta have not been directly assessed. Using immunogold electron microscopy, we determined that transferrin receptor is concentrated on the intracellular vesicles in syncytiotrophoblast I while ferroportin 1 is on the basal membrane of syncytiotrophoblast II. Fluorescent imaging of maternally injected transferrin iron in the placentas collected at 6 time points postinjection (n = 1–3 animals/time point) showed that transferrin iron was taken up and metabolized within syncytiotrophoblast I within 48 h after injection. These data indicate that the intracellular iron-trafficking mechanism is distinct in different placental cells.