[Placental deposition and transfer of iron dextran to fetuses in mice at near term].

Deposition of iron dextran particles in the fetoplacental system was investigated by light and electron microscopy after intravenous injection into pregnant mice on days 18-19 of gestation. Thirty minutes after injection, the labyrinth trophoblast cells were strongly positive for iron whereas the fetal capillary endothelium was weakly stained. Electron microscopy revealed the transfer of iron dextran particles to the intercellular space between the first and second layers of trophoblasts, as well as within the vacuoles of the second layer trophoblasts. Transport through the second layer trophoblasts, however, was not evidenced, suggesting that the trophoblast layer may constitute a significant barrier. Three hours after injection, heavy iron reaction was observed in Reichert's membrane, trophoblast cells lined with this membrane, and visceral yolk sac. Electron microscopic examination of parietal yolk sac revealed the aggregation of iron dextran particles in the trophoblast cells with little penetration into the Reichert's membrane and parietal endoderm, suggesting that the Reichert's membrane and adhering trophoblast cells may be a significant barrier for selective transport of particulate materials in the yolk sac placenta.