BLOCKADE OF ALFA AND BETA-ADRENERGIC RECEPTORS CAN PREVENT STIMULATION OF LIVER ORNITHINE DECARBOXYLASE ACTIVITY BY GLUCOCORTICOID AND LAPARATOMY

Rat liver ornithine decarboxylase induction by dexamethasone or laparatomy, which is dramatically impaired by catecholamine depletion, is not affected by alpha-and beta -adrenergic blockers administered simultaneously 1 h prior to steroid injection or operation. However, if blockade is maintained for 24 h, an effect comparable to that of catecholamine depletion is obtained. Reciprocally, the response of the decarboxylase to catecholamines is severely compromised in adrenalectomized rats. Under the same conditions, induction of tyrosine aminotransferase by dexamethasone is not significantly affected by catecholamine availability, which altogether demonstrates that rat liver ornithine decarboxylase activity is specifically governed by the interaction between glucocorticoids and catecholamines.