Localization and characterization of EGF/TGF-α receptors on peri-implantation trophoblast in sheep

Receptors for epidermal growth factor (EGF) have been identified on the ovine trophoblast as early as day 15 of gestation. A radioligand assay with 125 I-labelled EGF was used to detect high and low affinity binding sites on the trophoblastic and placental membranes. The binding of 125 I-labelled EGF was inhibited by increasing concentrations of unlabelled EGF. Competition studies with other peptide hormones including transforming growth factor α (TGF-α), insulin-like growth factor-I (IGF-I) and ovine placental lactogen confirmed the specificity of EGF/TGF-α for its receptor