EPIDERMAL GROWTH-FACTOR AND ITS RECEPTOR GENE-EXPRESSION AND PEPTIDE LOCALIZATION IN PORCINE OVARIAN FOLLICLES

The present study was undertaken to determine the expression of genes for epidermal growth factor (EGF) and its receptor (EGF-R) in various components of medium-sized porcine ovarian follicles by reverse transc ription-polymerase chain reaction (RT-PCR), and to localize their pept ides during folliculogenesis by immunocytochemistry. A strong band for EGF mRNA transcript was detected in the oocyte, whereas the signal in cumulus, granulosa, and theca cells was very weak but detectable. In contrast, a very strong EGF-R mRNA signal was observed in cumulus, gra nulosa, and theca cells, whereas the signal in the oocyte was very wea k. EGF peptide was localized ill the oocyte, cumulus, and granulosa ce lls of all stages of follicle. In the oocyte, the intensity of immunos taining was more pronounced in primordial and primary follicles, compa red to antral follicles. In large antral follicles, immunostaining was pronounced in granulosa cells, whereas theca cells showed little or n o detectable staining for EGF. EGF staining was also observed in the c umulus and granulosa cells of follicles undergoing atresia. EGF-R immu nostaining was observed in the oocytes of primordial and primary folli cles, and in cumulus, granulosa, and theca cells of all stages of foll icle, including atretic follicles. In large antral follicles, the inte nsity of immunostaining was more pronounced in theca cells than in gra nulosa cells, and the oocyte showed little or no detectable staining. No immunostaining was observed when the primary antibody was replaced with preimmune serum (EGF), or preabsorbed with the control peptide (E GF-R), confirming the specificity of the staining procedures. These re sults suggest a local follicular production of EGF and its receptor in the porcine ovary, and thus a role for EGF of follicular origin in th e regulation of follicular development in autocrine/paracrine fashion. (C) 1995 Wiley-Liss, Inc.