Presence of neurophysin-like material in the pituitary corticotrophs and melanotrophs and cells of the arcuate nucleus of the rat as revealed by immunocytochemistry.

Highly purified porcine neurophysin-II, prepared from pig posterior pituitary lobe tissue was injected into fifteen rabbits in the preparation of anti-neurophysin sera. All antisera, when used in association with immunohistochemical procedures, gave an immunoreaction in structures of the rat hypothalamo-neurohypophysial system. Four antisera, however, also stained cells of the arcuate nucleus, corticotrophs and melanotrophs. Staining of the latter two cell groups also occurred in tissues obtained from Brattleboro rats. Preadsorption of the latter neurophysin antisera with either alpha-MSH, beta-LPH, beta-endorphin, ACTH (1-24), ACTH (17-39), ACTH (1-39), gastrin and CCK, failed to inhibit the staining of the corticotrophs, melanotrophs and cells of the arcuate nucleus. Inhibition of staining was achieved only by preadsorption of the antineurophysin sera with the neurophysin antigen or an homogenate prepared from the anterior pituitary. These results support the observation by others that the biosynthesis of the ACTH-beta-endorphin system in the pituitary and hypothalamus may also be accompanied by the appearance of neurophysin.