Objective　The effects of nitric oxide(NO) on the endotoxin-induced tissue damage,especially intestinal injury and bacterial translocation are still poorly known, although its involvement in vasodilatation and hypotenion in shock is much clear. So, the intestinal damage and bacterial translocation were observed in this study in endotoxemic rats after treatment with Nω-nitro-L-arginine(LNNA),the special inhibitor of NO synthase(NOS),and L-arginine,the substrate of NOS.Methods　The endotoxemia was conducted with administration of lipopolysaccharide(O111B4,10mg/kg,i.p.),animals were treated with LNNA(4mg/kg,i.p.)or L-arg(40mg/kg,i.p.).Intestinal molondialdehyde(MDA) content and Diamine oxidase(DAO) activity were determined,and mesenteric lymph nodes were cultured.Results　The results showed that endotoxin decreased intestinal DAO acitivity but increased MDA content and incidence of bacterial translocation to mesenteric lymph nodes.These effects of endotoxin were aggregated by inhibition of NO production with LNNA, but attenuated by L-arg.Conclusion　We concluded that inhibition of NO formation might enhance endotoxin-induced intestinal damage and bacterial translocation,which suggested that NO might play a protective role in this endotoxemia model.