ADRENAL CORTICOSTEROID INVOLVEMENT IN CONTROL OF LIVER GLYCOGEN PHOSPHORYLASE ACTIVITY

Adrenalectomy results in a marked decrease in the hyperglycemic effects of administered epinephrine and cyclic AMP. The absence of an effect with cyclic AMP suggests that the metabolic lesion resides beyond adenyl cyclase, possibly at the level of the liver phosphorylase reaction. Lack of adrenal corticosteroids results in no change in the levels of active liver glycogen phosphorylase. However, the levels of inactive enzyme are greatly diminished. Epinephrine or cyclic AMP administration does not result in activation of available inactive enzyme. Hydrocortisone replacement therapy results in restoration of inactive liver phosphorylase levels and return of the hyperglycemic effects of epinephrine and cyclic AMP. It is proposed that adrenal corticosteroids have a role in maintaining physiological phosphorylase levels and in the conversion of inactive to active phosphorylase, possibly at the level of the phosphorylase kinase kinase reaction. © 1969.