Epidermal growth factor receptors in uteroplacental tissues in term pregnancy before and after the onset of labor.

Using saturation binding assays and Scatchard analyses, we determined the concentrations and binding affinities of epidermal growth factor (EGF) receptors in human myometrium (n = 13) and decidua (n = 10) before and during labor and in placenta (n = 15), chorion (n = 17), and amnion (n = 17) before labor, during labor, and after vaginal delivery. Each tissue was individually assayed. In myometrium and chorion, EGF receptors increased significantly from 5.6 +/- 0.8 and 13.5 +/- 1.7 fmol/mg protein (mean +/- SEM) before labor to 11.1 +/- 2.8 and 26.7 +/- 3.0 fmol/mg protein, respectively, after the onset of labor (P < 0.05). In amnion, EGF receptors increased from 12.8 +/- 2.7 fmol/mg protein before labor to 33.0 +/- 2.3 fmol/mg protein during labor, but decreased significantly (5.9 +/- 1.2 fmol/mg protein) with vaginal delivery (P < 0.05). Decidual and placental concentrations of EGF receptors did not change significantly with labor. The binding affinity of EGF receptors in all tissues studied did not change significantly with labor, as reflected by their respective association and dissociation constants. Up-regulation of EGF receptors in myometrium, chorion, and amnion with spontaneous labor may enhance stimulation of prostanoid production and stimulate uterine activity.