Somatostatin in the ovary of an African lungfish (Protopterus annectens): an in situ hybridisation, immunohistochemical and autoradiographical study.

In mammals, somatostatin seems to be involved in the control of ovarian steroidogenesis. There have been no studies on the presence or actions of somatostatin in the ovary of nonmammalian vertebrates. The localisation of somatostatin-14 was examined immunohistochemically using the antibody to somatostatin-14 in the ovary of the African lungfish Protopterus annectens. Immunoreactivity was present in the granulosa cells of mature ovarian follicle examined by light microscopy. Using an oligonucleotide probe complementary to mRNA for somatostatin-14 and labelled at the 3'-end with alpha-35S, in situ hybridisation demonstrated somatostatin-14 mRNA distributed in cells showing the same localisation as that of the immunoreactive cells. Binding sites for SST-14 were identified with autoradiography using [125I]somatostatin-14. Binding sites were localised on granulosa and theca cells. Somatostatin-14 may be thus synthesised in the lungfish ovary.