Immunohistochemical Localization of ACTH and Prolactin in the Pituitary Gland of Adult Migratory Sockeye Salmon (Oncorhynchus nerka)

Abstract

Antibodies to porcine adrenocorticotrophic hormone (ACTH), Synacthen (synthetic corticotrophin, Ciba), and ovine prolactin were prepared in rabbits and the antisera were tested for specificity against several pituitary hormones. The gamma-globulin fractions of the antisera were conjugated with fluorescein isothiocyanate and the labelled antibodies were "purified" by column chromatography.Fresh-frozen sections of pituitary glands of adult migratory sockeye salmon were incubated with the antibody solutions and examined with a fluorescence microscope. The resulting antigen–antibody complex could be localized by re-photographing the same or alternate sections after fixation and staining. Anti-ACTH and anti-Synacthen appeared to be bound specifically by the epsilon cells, whereas anti-prolactin reacted with the eta cells of the rostral pars distalis. Pituitary glands collected at various stations along the migratory route, including one seawater sample, showed the same reactivity. Other glands were prepared for histological examination. Microspectrophotometric analysis of cell types showed that the granule density of the ACTH cells increased gradually during the later part of migration. In the prolactin cells, no change in granulation could be detected during entrance into the river or subsequent spawning migration.