Electron microscopic findings in rat hypophysis after adrenalectomy and administration of ACTH. I. Adenohypophysis.

Ultrastructural changes in the secretory lobe of rat hypophysis following bilateral adrenalectomy and a single subcutaneous administration of 1 i.u. of ACTH were studied. Both after adrenalectomy and ACTH administration, ultrastructural changes were found to appear exclusively in one type of secretory cells. After adrenalectomy, pictures were found in these cells indicative of increased synthesis of the secretory granulations. One hour after the administration of ACTH the ACTH-secreting cells showed features of decreased secretory activity.