Abstract： Objective To investigate the protective effects of endotoxin precondition on hepatic tissue in rats with endotoxemia.Method The models of rats with acute endotoxemia were produced by injecting LPS directly.Seventy-two male wistar rats were randomly divided into three groups:saline control group(N,n=24),lipopolysaccharide (LPS)-treated group(L,n=24),LPS pretreated group(P,n=24).Each group was divid-ed into four subgroups:saline control and lipopolysaccharide (LPS)-treated 2 h,4 h,6 h,12 h groups and LPS-pretreated 2 h,4 h,6 h,12 h groups.Rats in group P were first administered with introperitoneal injection of 0.25 mg/kg LPS,and after 24 hours,the rats were injected with 0.5 mg/kg LPS.Rats in group N and group L received with an equivalent amount of saline.After 72 hours,rats in group L and group P were intravenonsly injected with 10 mg/kg LPS,and rats in group N received with an equivalent amount of saline.Six rats were killed at 2,4,6 and 12 hours after injection of LPS in group L and P.The hvers were removed for detecting Toll like receptor-4 (TLR-4),nuclear factor-кB(NF-кB),tumor Necrosis Factor-apha(TNF-α)and malondialdehyde(MDA).The blood was drawn for detecting Alamine aminotmnsferose (ALT) and Aspartate aminotransferose (AST).The patho-logical changes of liver were also examined.Software SPSS13.0 was utilized to do ANOVA for statistical analysis.Results The rats exposed to LPS alone demonstrated an increase in TLR-4.NF-кB and TNF-α activity of the liver tissue.Incontrast.the rats exporsed 10 LPS prelreatment exhibited a significant decrease in TLT-4,NF-кB and TNF-α activity.The contents of TLR-4,NF-кB and TNF-α of LPS-treated 4 h groupwere,(38.76±0.67),170.82 ±31.40),293.16±49.49)and(6.263±0.351),significantly higher than those of the saline control group.The administration of endotoxin pretreatment reduced the indexes to(22.35±1.35),(135.55±26.44)and(234.23±44.96),respectively(P＜0.05).Conclusions TLR-4,NF-кB and TNF-α take part in the progress of hepatic injury in rats with endotoxemia.Endotoxin pretreatment can eliminate hepatic injury and protect the hepatic tissue by downmgulating the levels of TLR-4.NF-кB and TNF-α.