Transforming Growth Factor-Alpha in the Adult Bovine Ovary: Identification in Growing Ovarian Follicles1

Abstract

The pituitary gonadotropins and gonadal steroids are required for normal follicular growth and development but neither has been shown to act directly as a granulosa cell mitogen in vitro. A number of polypeptide growth factors, however, are known to have pronounced mitogenic effects on the cells of the follicle. We have localized transforming growth factor-alpha (TGF-.alpha.), a potent mitogen, in bovine thecal cells via immunoperoxidase staining using a monoclonal antibody for TGF-.alpha. that does not cross-react with epidermal growth factor. TGF-.alpha. staining is most intense in the theca of follicles at the discrete physiological stages know to shown rapid granulosa cell growth (small follicles of 0.7-2.0 mm diameter). Staining intensity for TGF-.alpha. declines in large preovulatory follicles, coincident with the known decline in granulosa cell mitosis. These studies provides further evidence for paracrine interactions in the ovary and show that TGF-.alpha. may play an important role in the regulation of follicular development in the adult bovine ovary.