A study of the immunohistochemical localization of the progesterone and oestrogen receptors in the magnum of the immature ostrich, Struthio camelus.

The immunolocalization of the progesterone (PR) and oestrogen receptors (OR), in the magnum of the immature ostrich, was investigated during periods of ovarian activity and inactivity. In the immature ostrich, with an active ovary, numerous well-developed tubular glands were present in the lamina propria. Significantly, PR immunostaining was strong in the surface epithelium and tubular glands of these birds. In contrast, weak staining for the PR was observed in the surface epithelium of birds with inactive ovaries. Tubular gland formation, in these birds, was indicated by bud-like invaginations of the surface epithelium. Oestrogen receptor immunoreactivity was negligible in both birds with active and inactive ovaries. These findings suggest that steroid hormones, produced by the active ovary of the immature ostrich, influence the differentiation of the magnum. Furthermore, the action of these steroid hormones appears to be mediated through the PR.