Adrenocorticotropic hormone-releasing activities of interleukins in a homologous invivo system

We compared adrenocorticotropin-releasing activities of several interleukins in a homologous or heterologous in vivo system. Intravenous injection of rat interleukin-1 α significantly increased plasma adrenocorticotropin in conscious, freely-moving rats 30 min after the injection, and the effect was 10 times greater than that of human interleukin-1 α. Rat interleukin-2 affected plasma adrenocorticotropin in a much slower manner and increased its levels significantly 120 min after the injection. Human interleukin-2 had no effect on plasma adrenocorticotropin. Thus, species difference in the experimental system should be considered to assess the physiological significance of cytokines in the neuroendocrine system.