Regulation of Glycogen Metabolism in the Adrenal Gland. III. Hormonal Effectsin Vivo

The in vivo hormonal regulation of the adrenal glycogen level has been studied in normally fed and fasted rats. It was found that a 24-hr starvation increases the glycogen level 2- fold, and that this can be decreased again, either in intact or in hypophysectomized rats, by administration of epinephrine, glucagon, glucose, insulin, or ACTH. Anti-insulin serum blocks the effect of epinephrine, glucagon and glucose, suggesting that they act in the adrenals via insulin. ACTH, on the other hand, can deplete adrenal glycogen independently of insulin, and its action is apparently not mediated by corticoids. The depleting effect of insulin upon adrenal glycogen can be dissociated from its action on glycemia. Acute or chronic insulin deficiency, but not of pituitary factors, produces an increase of the glycogen level in normally fed rats. Thus, this hormone seems to play an important role in the maintenance of the adrenal glycogen level. These results indicate that the hormonal regulation of glycogen metabolism in the adrenal gland differs from that operating in other tissues. In fact, epinephrine and glucagon, which are usually glycogenolytic, have no such effect in the adrenal under the conditions used. In addition, insulin— a normally glycogenic hormone—is glycogenolytic in the adrenal gland. The significance of these observations is discussed. (Endocrinology88: 233,1971)