CELLULAR-LOCALIZATION OF IMMUNOREACTIVE EPIDERMAL GROWTH-FACTOR DURING WOLFFIAN DUCT DIFFERENTIATION OF THE FETAL MOUSE

Previous studies from this laboratory indicated a role for epidermal g rowth factor (EGF) in androgen-dependent male reproductive tract diffe rentiation of the fetal mouse. Expression of an EGF-like protein durin g Wolffian duct differentiation was indicated from the determinations by radioimmunoassay (RIA) and radioreceptor assay. To further characte rize the protein and to assess its role in male sexual differentiation , expression of the protein has been analyzed by Western blot assay an d its tissue-specific cellular expression has been determined by immun ocytochemical assay in the present study. Western blot analysis of the 18-day fetal male reproductive tract detected an immunoreactive band of the predicted 6-kDa size. Immunocytochemical analysis also detected EGF-specific immunostaining in the Wolffian duct derivatives. At day 18 of gestation, the staining was localized predominantly in the epith elial nuclei of the Wolffian duct derivatives whereas at days 14 and 1 6 of gestation, the staining was equally distributed in the mesenchyma l and epithelial sites of the Wolffian duct derivative. The intensity of the staining increased with progression of differentiation during t he 14th-18th days of gestation. Prenatal exposure to the antiandrogen flutamide significantly reduced the immunostaining of the duct. Thus, a role for EGF in Wolffian duct differentiation is indicated.