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Abstract

This study demonstrates the ability of pituitary anlagen from 12- and 15-day embryonic rats to undergo cytodifferentiation in a site distant from that of its normal juxtaposition with the hypothalamus.

Pituitary anlagen (PA) were isografted from 12- and 15-day-old embryonic donors to under the kidney capsule of intact adult female rats. Seventeen days later the grafts were recovered and processed for light and electron microscopy (LM and EM). Four of six 12-day and all five 15-day PA grafts developed into adenohypophyseal-like tissues. At the light as well as EM level, no consistent quantifiable differences could be detected between the glandular tissues that developed from the two different donor groups. While most of the cells within anterior pituitary-like tissue were chromophobic at the LM level, some cells were stained positive with periodic acid-Schiff and Orange G. Examination by EM revealed that most cells within the glandular portions of the grafts were granular and that these cells could be grouped into three general categories based on their secretory granule morphology. The sizes of the secretory granules ranged from 150-550 nm in diameter. Clear examples of exocytosis of the granules were evident in grafts of both 12- and 15-day PA, usually in areas of the graft that were more vascularized. In some cells exocytosis was extensive. Agranular cells in the graft parenchyma included follicular and undifferentiated cells.

The results of this investigation suggest that kidney capsule grafts may prove useful in elucidating the factors that influence pituitary development.