STRESS-INDUCED CHANGES IN BLOOD LEUKOCYTE DISTRIBUTION - ROLE OF ADRENAL-STEROID HORMONES

The numbers and proportions of leukocytes in the blood provide an impo rtant representation of the state of activation of the immune system, and of the pattern of distribution of immune cells in the body, We hav e shown previously that acute stress induces large, rapid, and reversi ble changes in the distribution of peripheral blood leukocyte subpopul ations in the rat, The studies described here specifically investigate the role played by adrenal steroid hormones in mediating stress-induc ed changes in blood leukocyte distribution, Since adrenal steroids act at two distinct receptor subtypes that show a heterogeneity of expres sion in immune cells and tissues, the role played by each subtype in m ediating changes in leukocyte distribution is also investigated, Cyano ketone, a corticosterone (CORT) synthesis inhibitor, significantly red uced the decrease in lymphocyte numbers observed during stress and sig nificantly enhanced the increase in neutrophil numbers observed after the cessation of stress, Acute administration of aldosterone (a specif ic type I adrenal steroid receptor agonist) to adrenalectomized animal s did not have a significant effect on blood leukocyte numbers, In con trast, acute administration of CORT (the endogenous type I and type II receptor agonist), or RU28362 (a specific type II receptor agonist), to adrenalectomized animals produced changes in leukocyte distribution that were similar to those observed in intact animals during stress, These results suggest that CORT, acting at the type II adrenal steroid receptor, is a major mediator of the stress-induced changes in blood lymphocyte and monocyte distribution.