Ultrastructural features of adenohypophysis of normal and ovariectomized rats

ABSTRACT

Electron microscopic study of the control adenohypophysis revealed six different cell types. Somatotrophs were the most frequently observed cells with large, spherical, uniform electron dense secretory granules. The corticotrophs were large or medium sized cells with marginal granules. The gonadotrophs were identified with small granules, variable in size, shape, density and distributed throughout the cytoplasm. The mammotrophs were large cells with the largest secretory granules with variable heterogenecity. While the thyrotrophs were identified as small, irregular polygonal cells with the smallest marginal secretory granules. Lastly, the chromophobes were agranulated cells with little cytoplasm. In ovariectomized rats, the main ultrastructural changes were increased number of gonadotrophs with marked vacuolation of cytoplasm and the nuclei were eccentric in some cells, shrunken or dissoluted in others. The secretory granules were markedly decreased or even degranulation in some cells. Signs of activation of the cell organoids were indicated by dilated RER swollen mitochondria, increased number of lysosomes, and the nuclei were mainly formed of euchromatin.The other type of cells were less markedly involved. The previous results indicated that the gonadotrophs were the mainly involved cells in adenohypophysis regulated the ovarian pituitary function and after ovariectomy they showed hyperactivation to compensate the hormonal feed-back mechanism