Immunolocalization of alpha-fetoprotein in the ovary and hypophysis of immature female rats.

Alpha-fetoprotein (AFP), an oestrogen-binding protein, has been localized in the ovary and hypophysis of prepuberal rats. In the ovary, AFP was localized in secondary follicles, its distribution being limited to the liquor folliculi and the zona pellucida. In the hypophysis, AFP was only found in blood vessels. The intra-ovarian localization of the protein is consistent with our previous hypothesis that AFP might act as a regulator of ovarian activity by decreasing the local free oestradiol level.