Cytokines in the hypophysis: a comparative look at interleukin-6 in the porcine anterior pituitary gland.

Abstract

Interleukin-6 (IL-6) is a multifunctional cytokine produced by a variety of cell types in tissues of both the immune and endocrine systems. Among the major functions described for IL-6 are its role in the maturation of B cells to high-output antibody-producing cells and its contribution to the acute physiological responses to infection and inflammation, notably production of hepatic acute phase proteins and activation of the hypothalamic-pituitary-adrenal axis. In addition to these better known functions, IL-6 recently has been found within the pituitary of laboratory rats and also in the human pituitary. In rats, pituitary IL-6 mRNA is upregulated by peripheral exposure to bacterial endotoxin. However, the role of anterior pituitary IL-6 in host responses to infection and inflammation remains uncertain, although it may regulate pituitary hormone secretion. The following brief review summarizes the information available concerning cytokine production within the anterior pituitary of species of domestic livestock. To our knowledge, experiments conducted in our laboratory evaluating regulation of IL-6 mRNA expression and secretion from the porcine anterior pituitary provide most of the data in domestic species confirming the presence of IL-6 in the pituitary. Our data indicate that IL-6 mRNA is present in cultured porcine anterior pituitary cells and that the pituitary directly responds to stimulation with bacterial endotoxin by increasing secretion of IL-6. Furthermore, endotoxin-induced upregulation of IL-6 mRNA expression and secretion appears to be dependent upon production of cyclooxygenase products of arachidonic acid metabolism.