Immunohistochemical localization of epidermal growth factor receptors, epidermal-growth-factor-like and transforming-growth-factor-alpha-like peptides in chicken ovarian follicles

The purpose of this study was to determine the presence of epidermal growth factor receptor and its potential ligands epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) in the tissues of the maturing follicles in the ovary of laying ISA-Brown hens using peptide-specific immunohistochemical methods. Cryostat sections, 6-8 microns thick, were made from fresh-frozen tissues of F1-F4 (largest to fourth largest) and large white follicles and they were immunostained for epidermal growth factor receptor, epidermal growth factor or transforming growth factor alpha using specific polyclonal antibodies. The EGF receptor and both ligands were detected in the granulosa, theca interna and theca externa layers of the follicles. The EGF receptor was localized both in the plasma membrane and cytoplasm of all cell types. EGF was predominantly cytosolic, whereas TGF-alpha was found in the plasma membranes and perinuclear areas of all cell types. The concentration of the receptor and both ligands decreased with follicular maturation. This observation is consistent with our previous observation that the response to EGF and TGF-alpha decreases as follicles mature, and thus provides further evidence that the receptor or the ligands may have a regulatory role in avian ovarian function.