Abstract： Objective To investigate effects of low concentration carbon monoxide(CO) inhalation onrat with multiple organ(lung and intestine) injury induced by lipopolysaccharide(LPS).Methods Seventy-two male Sprague-Dawley rats were randomly divided into 4 groups:control(A),CO inhalation alone(B),LPS injection(C) and LPS injection+CO inhalation(D)groups.After 1h of LPS or an equal volume ofnormal saline administration by tail vein.the rats in C group exposed to room air after an intravenous injection of 5 mg/kg body weight LPS.the rats in B group were exposed to 2.5×10-4 CO simply,the rats in D group were intravenously injected 5 mg/kg body weight LPS and exposed to 2.5×10-4 CO continuously,and the rats in A grouP were also exposed to room air.All rats were sacrificed by exsanguination at 1,3 and 6 hours after observation.Lung and intestine tissues were homogenized for determination the levels of lung tumor necrosis factor-α(TNF-α),interlukin-6(IL-6),interlukin-10(IL-10),intestine platelet activator(PAF),intercellular adhesion molecule-1(ICAM-1)and IL-10 with enzyme-lined immunosorbent assay,the maleic dialdehyde (MDA)content.myeloperoxidase(MPO) and superoxide dismutase (SOD) activity with chemical colorimetric method.the extent of cell apoptosis with flow cytometery,the expression level of the heme oxygenase-1(HO-1) gene with semi-quantitative reverse transcription-polymerase chain reaction and the histology with light microscopy.Results Compared with both A and B groups at the same time point,the TNF-α,IL-6,PAF, ICAM-1,MDA,MPO and cell apoptosis rate of C group were increased(all P＜0.05),while IL-10 and SOD decreased(all P＜0.05),lung and intestine damage was remarkable.Moreover,with prolonging of time,the cell apoptosis rate in C group increased.As compared with C group at the same time point,the TNF-α,IL-6, PAF,ICAM-1,MDA,MPO and cell apoptosis rate of D group was decreased(all P＜0.05),while IL-10 and SOD increased(all P＜0.05),organ damage was obviously ameliorated.There were no statistical differences between A and B groups and between the different time point of same one group.Conclusions Low concentration CO inhalation could protect rat lung and intestine from LPS-induced injury via suppressing cell apoptosis,regulating the disorder of oxidant-antioxidant and imflammation-antiinflammation.