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 prolactin (PRL)-producing cells allowed us to define more precisely hypophyseal cytology in summer and winter animals and to study its modifications in the ectopic pituitary autograft, namely in a situation in which hypothalamic control is abolished. In the normal adenohypophysis, PRL-cells are preferentially localized in the an- teroventral region; in the autograft, 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 in summer. These results are in agreement with previous data (increase in fin caudal height, a PRL- dependent character, and in body weight) and demonstrate that, PRL hypophyseal secretion in Triturus carnifex comes under a temperature-dependent hypothalamic inhibitory control, active only in summer.