Epidermal growth factor and epidermal growth factor receptor in the ovary of the domestic cat (Felis catus)

Identification of epidermal growth factor (EGF) and its distribution in the ovary were examined with an immunohistochemical technique using a polyclonal rabbit antibody against mouse EGF. A combination of HPLC and enzymeimmunoassay was elaborated to quantify EGF in different compartments of the feline ovary. In addition, EGF receptors were localized in ovarian cryostat sections with a new ligand-histochemical technique using biotinylated EGF for labelling. Epidermal growth factor was present in theca interna cells, in specific aggregations of interstitial gland cells located next to tertiary follicles, in smaller, single cells of the ovarian cortex, and in the corpus luteum. The strongest EGF-positive reaction was found in vacuolized cells of the interstitium and in theca interna cells of large tertiary follicles rich in cytoplasm. The strictly cellular localization of the EGF-antibody reaction suggests the synthesis of EGF in these cells. Specific binding sites of EGF were present on granulosa cells of secondary and tertiary follicles and on interstitial gland cells. The EGF-binding capacity of granulosa cells of the cumulus oophorus was greater than that of the mural granulosa cells. Granulosa cells of atretic follicles showed a lower or no affinity for staining. In conclusion, we suggest that EGF plays an important role in ovarian folliculogenesis in cats.