In vivo effects of catecholamines and glucocorticoids on mouse thymic cAMP content and thymolysis

In vivo administration of the beta-adrenergic agonist, isoproterenol, induced a rapid, dose-dependent increase in the mouse thymic cyclic AMP (cAMP) content. Hydrocortisone (1 mg/animal), at a concentration which by itself did not alter the cAMP content of the thymus, markedly potentiated the effect of isoproterenol (5 micrograms/animal). Isoproterenol or hydrocortisone treatment led to a significant decrease in thymic weight and an even greater decrease in thymocyte number. In addition, the simultaneous administration of both agents produced additive effects on thymic atrophy. It appears from these results that glucocorticoids and catecholamines exert a negative control on the thymic size by increasing the programmed cell death of some cell subpopulations. Thus, glucocorticoids and catecholamines, either alone or in association, may influence the immune system under physiological or pathophysiological conditions.