PITUITARY IMMUNOCYTOCHEMISTRY AND PROLACTIN PLASMA-LEVELS IN HYPOPHYSECTOMIZED FEMALE NEWTS, TRITURUS-CARNIFEX, BEARING A LONG-TERM PITUITARY AUTOGRAFT

The use of specific immunocytochemical techniques to identify prolacti n (PRL)-producing cells allowed us to define more precisely hypophysea l cytology in summer and winter animals and to study its modifications in the ectopic pituitary autograft, namely in a situation in which hy pothalamic control is abolished. In the normal adenohypophysis, PRL-ce lls are preferentially localized in the anteroventral region; in the a utograft, these cells are well preserved and a radioimmunoassay (RIA) for amphibian PRL shows that PRL secretion, compared with that of the adenohypophysis in situ, does not vary in winter, while it increases i n summer. These results are in agreement with previous data (increase in fin caudal height, a PRL-dependent character, and in body weight) a nd demonstrate that, PRL hypophyseal secretion in Triturus carnifex co mes under a temperature-dependent hypothalamic inhibitory control, act ive only in summer.