Studies on the placental transport mechanism for iron.

Transferrin (Tf) and ferritin (Fr), the proteins which participate in iron transport, were examined to determine their fluctuation during pregnancy and their localization in human placental tissue, and the iron transport mechanism between mother and fetus was discussed. The main results are as follows: Maternal serum ferritin (SFr) decreased remarkably and the maternal total iron binding capacity (TIBC) increased gradually as pregnancy progressed. Maternal serum iron (SI), SFr and TIBC at delivery were 59.8 +/- 26.2 micrograms/dl, 9.6 +/- 7.2 ng/ml and 495.2 +/- 100.3 micrograms/dl, and cord blood SI, SFr and TIBC were 161.5 +/- 42.1 micrograms/dl, 160.5 +/- 67.2 ng/ml and 177.7 +/- 33.9 micrograms/dl, respectively. Peroxidase conjugating antibody method revealed the localization of Tf on the microvillous surface of syncytiotrophoblasts, and the localization of Fr in all layers of trophoblasts, especially in the neighborhood of the surface. Ferritin content of the placenta in the 1st, 2nd and 3rd trimesters was 0.07 +/- 0.03, 0.18 +/- 0.03 and 0.25 +/- 0.09 (micrograms/mg protein), respectively. These results indicate that iron is transferred from the mother to the fetus by the placental active function, and Tf receptor and Fr on trophoblasts participate in the adequate placental iron transport.