The pituitary cleft of the rat: an electron microscopic study.

The epithelium of the pituitary cleft and its colloid have been studied at the ultrastructural level in normal, adrenalectomized, castrated, dehydrated and lactating adult rats. Both control and experimental animals showed cells in different stages of degradation inside the cleft and mixed with the colloid. These exfoliated cells seems to have originated from the cleft's epithelium of the adjacent granular cells. In adrenalectomized and castrated rats the rostral epithelium of the cleft had large intercellular spaces that in some instances appeared to open directly into the cleft. Occasionally, the adenohypophysial canaliculi of the adrenalectomized rats were also seen connecting with the cleft. In lactating and castrated animals dark cells appeared more frequently in the rostral and caudal epithelium of the cleft. The results obtained suggest that the colloids is originated at least in part by involuted pituitary cells. There is also evidence that the follicular cavities of the Pars distalis and the cleft are continuous structures.