STUDIES ON THE CORTICAL CONTROL OF THE ADRENAL MEDULLA IN THE RAT

¹ Department of Pharmacology and Section of Nuclear Medicine, The University of Chicago, Chicago, Illinois

Morphologic and biochemical changes in the adrenal medulla of rats were followed with time after hypophysectomy. Phenylethanolamine-N-methyl transferase (PNMT) activity decreased very rapidly; i.e., there was a 50% fall within about 4 days. The decline in epinephrine concentration was gradual; epinephrine concentration had decreased by one-half in 50 days. With the light microscope, an increase in the size of the islets of norepinephrine-containing cells was seen on the periphery of the adrenal medulla 50 days after surgery. Ultrastructurally, the decline in the average number of electron-dense granules was marked in epinephrine-containing cells. Hypertrophy of the rough endoplasmic reticulum and the Golgi apparatus was evident in cells almost devoid of granules. There was a correlation between the decline in the average number of granules per epinephrine cell and the fall in epinephrine concentration. Norepinephrine cells were less affected. Electron-dense granules of small size and the presence of both epinephrine and norepinephrine granules in one cell were seen from 17 days on after surgery. ACTH and dexamethasone treatment of hypophysectomized rats resulted in an increase in PNMT activity, epinephrine concentration and the average number of electron-dense granules in epinephrine as well as in an increase in the average number of granules in norepinephrine cells.