Regulation of Nutrient Transport across the Placenta
We examined the effects of epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) on the uptake of AIB by and its transfer across near-term human placental syncytiotrophoblast in two-sided culture. Pre-incubation of the trophoblast cell layer with either EGF (50ng/ml) or IGF-I (100ng/ml) on the apical (microvillous, in vivo maternal-facing) side reduced rates of unidirectional microvillous-to-basal transtrophoblast AIB transfer, increasing AIB retention within the cells. EGF on the basal (fetal-facing) side of the cell layer enhanced AIB uptake from the microvillous side but also increased overall mediated permeability in both directions. IGF-I at the basal surface, however, increased AIB uptake across the microvillous membrane, and induced a backflux from the cells into the basal medium dependent upon basal AIB concentration, suggesting that in vivo IGF-I on the fetal side enhances maternal-to-fetal placental transfer. The ideas are consistent with current concepts of maternal-placental and fetal-placental interactions regulating pregnancy and fetal development.