IMMOBILIZATION STRESS INCREASES HEPATIC IL-6 EXPRESSION IN MICE

When mice were subjected to restriction of movement in a small cylinde r (immobilization stress), the serum interleukin (IL)-6 level rose in 1 h, following increased expression of IL-6 mRNA in both the liver and the spleen. The IL-6 mRNA induction was much greater in the liver tha n in the spleen when compared on a whole-organ basis. Intraperitoneal injection of bacterial lipopolysaccharide (LPS) also increased IL-6 mR NA expression in these organs, but more preferentially in the spleen. Immunohistochemical examinations of liver tissue using an antibody aga inst murine IL-6 revealed that immobilization stress induced IL-6 main ly in hepatic parenchymal cells, whereas LPS injection did so only in sinusoidal mononuclear cells. These results indicate that immobilizati on stress induces IL-6 production in the liver, especially in hepatic parenchymal cells, probably by a different mechanism from that for IL- 6 induction by LPS. (C) 1997 Academic Press.