HISTOPHYSIOLOGY OF THE PITUITARY CLEFT AND COLLOID CYSTS IN THE ADENOHYPOPHYSIS OF THE RAT. CHANGES AFTER GONADECTOMY

1. Pituitaries of normal, adrenalectomized and castrated male rats have been studied using the freeze-drying technique. 2. The pituitary cleft is surrounded anteriorly by an endothelioid fenestrated epithelium and posteriorly by a cubical or cylindrical epithelium. In the latter colloid droplets can be seen in the cytoplasm, and evaginations containing colloid droplets occur at the apical poles of the cells and project into the lumen of the cleft. 3. The histological picture suggests that the colloid contained in the cleft might be formed by:(a) destruction of the basophilic and eosinophilic cells of the pars distalis, (b) transudation of plasma from capillaries in the anterior wall of the cleft, (c) mucus discharged by goblet cells in the anterior epithelium, and (d) apocrine secretion and the secretion of colloid from the posterior epithelium. 4. Changes in the height, the amount of cytoplasmic colloid and the apocrine secretion of the posterior epithelium occur after adrenalectomy and castration. 5. There are two types of cyst in the adenohypophysis, one having a mucinous content and covered with a mucous epithelium, and the other a flattened epithelium and a colloid content. The latter, in addition to the pituitary cleft, might play some part in secretory processes