Kazumaro Yamada

An electron microscopic study on the possible site of production of ACTH in the anterior pituitary of mice.

SummaryAn ultrastructural study has been made of a new cell type different from five known cell types in the anterior pituitary of normal mice. This new cell type is characterized by the special morphology of secretory granules. The immature form of the granules with high electron density in and around the Golgi area becomes vesiculated in the cell periphery. With glutaraldehyde-osmium fixation, however, the content of such vesiculated granules acquires electron density.In attempts to certify the independence of this cell type not related to the others and to elucidate its physiological function, a series of experiments has been made.After adrenalectomy the cell type exhibits a characteristic response represented by hypertrophy of the Golgi apparatus and prominent other cell organelles. Under the same condition the FSH-producing cell to be differentiated from the new cell type does not undergo any cytological changes. Instead, all FSH-producing cells show typical alterations at 100th day after orchidectomy, when the cell in question remains intact. Adrenalectomy following 100 day-orchidectomy causes a stimulative effect upon the new cell type. Furthermore, administration of hydrocortisone results in a hypofunctional state of this cell type.All these findings indicate that the new cell type identified in the present study is the site of ACTH production.