Protective Effects of Endotoxin Pretreatment on Lung Injury of Rats with Endotoxemia

Objective To investigate the protective effects of endotoxin pretreatment on lung injury of rats with endotoxemia.Methods The rat model of acute endotoxemia was established by injecting lipopolysaccharide(LPS) intraperitoneally.Seventy-two male Wistar rats were randomly divided into three groups,ie.a saline control group(N,n=24),a LPS-treated group(L,n=24),and a LPS pretreated group(P,n=24).Each group was divided into 2 h,4 h,6 h,and 12 h subgroups.The rats in group P were firstly administered with introperitoneal injection of 0.25 mg/kg LPS.After 24 hours,they were subjected to the injection of 0.5 mg/kg LPS.The rats in group N and L received injection of equivalent amount of saline.After 72 hours,the rats in group L and P were challenged with intravenous injection of 10 mg/kg LPS,otherwise saline in group N.Six rats were killed at 2,4,6 and 12 hours respectively after injection of LPS in group L and P.The lungs were removed for detecting intercellular adhesion molecule-1(ICAM-1),superoxide dismutase(SOD),and malondialdehyde(MDA).Meanwhile the level of tumor necrosis factor-alpha(TNF-α) in serum was measured,and the pathological changes of lung were also examined.Results The contents of ICAM-1,MDA and TNF-α in the LPS-treated 4 h group were 75.07±0.53,(3.93±0.42) μmol/g,and(478.62±45.58)pg/mL respectively,significantly higher than those in the saline control group.The endotoxin pretreatment reduced the above indexes to 42.40±0.44,(2.89±0.49) μmol/g and(376.76±43.67) pg/mL respectively(P0.05).The content of SOD in the LPS-treated 4 h group was(6.26±0.31) U/mg,significantly lower than that in the saline control group.The endotoxin pretreatment increased SOD to(8.79±0.35) U/mg.Conclusion Endotox in pretreatment can suppress the progress of lung injury in rats with endotoxemia and protect the lung tissue by down-regulating the inflammatory response and oxygen free radica l production.