Effects of gender and gonadectomy on ACTH response to interleukin-1 beta in the rat: Comparison with the modulation of ACTH response to immobilization stress

We examined the influence of gender and gonadectomy on the plasma adrenocorticotropin (ACTH) response to intravenous administration of human recombinant interleukin (IL)-1 beta (3 mu g/kg) in the rat. For comparison, we also examined whether gender and gonadectomy affect ACTH secretion after immobilization stress (a 30-min period), which is a nonimmunological stressor. IL-1 beta induced a significantly higher ACTH response in females than in males, and this sexual difference was abolished by gonadectomy in both sexes. By contrast, ACTH secretion after immobilization was statistically the same in males and females, but tended to be higher in gonadectomized males than in gonadectomized females. These results may suggest a dissociative regulation by gonadal steroids of IL-1 beta- and immobilization-induced ACTH responses in the rat. The sexual difference in ACTH response to IL-1 beta may represent another example of the sexually dimorphic immunological activity, which is known to be higher in females than in males.