EFFECTS OF CORTICOTROPHIN AND DEXAMETHASONE ON THE LEVELS OF CORTICOSTEROIDS, ADRENALINE AND NORADRENALINE IN THE ADRENAL GLANDS OF CATS

Abstract

SUMMARY The concentration of adrenaline, noradrenaline and corticosteroids in the adrenal glands of intact cats was studied after administration of corticotrophin (ACTH) or dexamethasone. The animals were treated with ACTH for 3, 7 or 14 consecutive days and killed 3 h (group A) or 24 h (group B) after the last injection. In group A the levels of corticosteroids were significantly increased. Significant decreases were found in group B. A significant decrease in noradrenaline concentration was found in all experiments after administration of both ACTH and dexamethasone. No significant change in the adrenaline level was observed after only 3 days of ACTH or dexamethasone administration, but significant decreases were obtained in both groups after injection of ACTH for 7 to 14 days. These findings suggest that the decrease in adrenal adrenaline may be secondary to the significant and greater decrease in adrenal noradrenaline and that in the intact cat the glucocorticoid levels, although regulating the activity of the adrenal enzyme for methylation of noradrenaline, may not be the only factor involved in the control of adrenaline production by the adrenal gland.