INTERLEUKIN-1 RECEPTOR ANTAGONIST PROTEIN AND MESSENGER-RNA IN THE RAT ADRENAL GLAND

The occurrence of the endogenous receptor antagonist for the cytokine interleukin-1 in the rat adrenal gland was analyzed by polymerase chai n reaction and by immunohistochemistry using a rabbit polyclonal antis erum. Expression of interleukin-1 receptor antagonist mRNA was demonst rated in both adrenal medulla and cortex, and a marked increase in the transcription was observed after systemic administration of lipopolys accharides. Interleukin-1 receptor antagonist immunoreactivity was see n in the adrenal medulla, and the immunofluorescence intensity was str onger in the adrenergic, phenylethanolamine N-methyltransferase-positi ve cells than in the noradrenergic chromaffin cells. The distribution of interleukin-l receptor antagonist protein is complementary to that of interleukin-1 alpha-like immunoreactivity found in phenylethanolami ne N-methyltransferase-negative cells and overlaps with and resembles the distribution of interleukin-1 beta-immunoreactive material. The ex pression of the interleukin-1 receptor antagonist in the adrenal gland complements previous findings of large constitutive pools of interleu kin-1 alpha and interleukin-1 beta in this neuroendocrine organ and al so suggests participation of adrenal interleukin-1 receptor antagonist in neuroimmune modulation.