Epidermal Growth Factor Binding to Human Amnion, Chorion, Decidua, and Placenta from Mid- and Term Pregnancy: Quantitative Light Microscopic Autoradiographic Studies

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Abstract
All of the cell types, but not noncellular elements, found in amnion, chorion, decidua, and placenta of midand term pregnancy contained numerous silver grains after incubation with 1 nM [125I]epidermal growth factor ([125I]EGF). These grains completely disappeared when excess unlabeled EGF, but not unlabeled insulin, was added with [125I]EGF, suggesting the presence of specific EGF receptors. Light cells of amnion contained more EGF receptors than dark cells of amnion, and the number of light cells decreased from mid- to term pregnancy. Numerous syncytiotrophoblasts containing a greater number of receptors than darkly stained cells in connective tissue were found in chorion from midpregnancy. The chorionic syncytiotrophoblasts were considerably reduced at term. Dark cells of decidua contained more receptors than light cells of decidua, and these cell numbers did not change during pregnancy. Placental syncytiotrophoblasts contained the EGF receptors. At mid- and term pregnancy, placenta contained the highest number of EGF receptors, followed by chorion > decidua > amnion. The receptor number in all tissues was higher at midcompared to term pregnancy. A decrease in number of cells as well as a decrease or fewer receptors per cell during pregnancy may explain the tissue and mid- vs. term pregnancy differences. The higher number of EGF receptors in amnion, chorion, decidua, and placenta at midpregnancy, at a time when the maternal and fetal blood EGF levels are at their peak, suggests that EGF may exert maximal biological effects on the feto-placental unit at midpregnancy.