[Ultrastructural localization of gonadoliberin in the gonadotropic cells of rat. Study by immunocytochemistry after cryo-ultramicrotomy (author's transl)].

By using ultrastructural immunocytochemistry after cryoultramicrotomy, gonadoliberin (GnRH) was localized in the gonadotropic cells of the female rat anterior pituitary gland. The immunocytological (IC) reaction was observed: (1) in the dense matrix of the secretory granules; (2) in the cytoplasmic matrix; (3) in the nucleus, in euchromatin, in the neighbourhood of heterochromatin. GnRH was seldom observed on the plasmic membrane. The values of the maximal dilution of the antibody (MDA) still giving an IC reaction decreased in the cytoplasmic matrix, in the nucleus and in the secretory granules. These observations, when compared with the data reported by biochemists, suggest that GnRH might be internalized in the gonadotropic cells. However, it remains to be shown that GnRH detected by IC reaction is specifically bound at binding sites.