Role of transferrin in iron transport between maternal and fetal circulations of a perfused lobule of human placenta

Abstract

The transfer of iron between the maternal and fetal circulations of an isolated perfused lobule of term human placenta was investigated using ¹²⁵I-labelled or ⁵⁹Fe-labelled diferric transferrin. There was negligible transplacental transfer of intact transferrin whereas nearly 4 per cent of the added ⁵⁹Fe was transferred into the fetal circulation after 2 h, where it became associated with fetal transferrin. Over 20 per cent of the added ⁵⁹Fe radioactivity was sequestered within the placental tissue during this period, associated with transferrin, ferritin and other uncharacterized molecules. This suggests an important role for an intracellular pool in regulating transfer. The presence of 10 mM chloroquine in the maternal circulation substantially reduced tissue accumulation of ⁵⁹Fe and totally inhibited transfer to the fetus. It is concluded that the initial stages of iron transfer to the fetus involve the internalization of maternal iron-saturated transferrin bound to membrane receptors by receptor-mediated endocytosis, which can be inhibited by the drug chloroquine. Subsequently, the transplacental transfer of iron to the fetus does not involve the concommitant movement of transferrin.