CORTICOSTERONE INDUCES HYPOACTIVITY OF PROLACTIN-IMMUNOREACTIVE CELLS

In order to determine whether corticosterone regulates activity of rat lactotrophs by acting directly at the pituitary level, immunohistoche mical studies were carried out in adrenalectomized rats, subjected or not to treatment with corticosterone or colchicine, and in monolayer c ultures after incubation with corticosterone. Adrenalectomy increased cellular and nuclear areas (p<0.01) of prolactin-immunoreactive cells without affecting their cytoplasmic area. Similar results were found i n adrenalectomized and colchicine-treated animals. Corticosterone reve rsed the effects of adrenalectomy, although normal values were partial ly reversed. In cultured pituitary cells, exposure to corticosterone r educed numerical density and cellular, cytoplasmic and nuclear areas w ith respect to control dishes. Morphological differences in shape, arr angement and nuclear features were observed after treatment with corti costerone. These results demonstrate an inhibitory effect of corticost erone on the activity of rat pituitary prolactin cells and suggest tha t corticosterone induces hypoactivity by acting on the pituitary prola ctin cells of male rats.