The Role of Transferrin in Placental Iron Transfer in the Rabbit

The role of transferrin in the process of iron uptake by the fœtus has been investigated in the pregnant rabbit. The specific binding of transferrin to the fœtal part of the placenta has been demonstrated using radioiodine labelled transferrin. Radioiodine labelled albumin was administered simultaneously to estimate and correct for the tissue distribution of transferrin due to the plasma content of the placenta. The capacity of the fœtal part of the placenta to bind transferrin increased markedly from the 15th to the 28th day of gestation, paralleling the sharp increase in the rate of iron transfer through the fœtal part with advancing pregnancy. Iron‐saturated transferrin was bound three times as avidly as iron‐free transferrin. The transferrin binding capacity of the fœtal part of the placenta was greater than that of the bone marrow, and far greater still than that of the maternal liver and spleen. There was no evidence for a specific binding to the placenta of transferrin present in the fœtal circulation.