Abstract： Objective To study the role of hydrogen sulfide(H2S)in the pathogenesis of acute lung injury (ALI)-induced oleic acid(OA)and its regulatory effects on the inflammatory msponse.Method The ALI models in SD rats were produced by intravenous injection of OA(0.1 ml/kg).Forty-nine male SD rats were divided into three groups randomly:control group,OA group and OA+sodium hydrosulfide(NaHS)group.Rats of OA group and OA+NaHS group were sacrificed at 2,4 and 6 hours after the administration of OA,respectively.Rats of control group were sacrificed at 6 hours after intravenous normal saline(0.1 ml/kg).PaO2,lung tissue wet/dry(W/D)ratio and IQA score were determined.The concentrations of H2S in lung tissue and plasma were tested by sensitive sulphur electrode.The IL-6.IL-8 and IL-10 levels were measured by doubleantibody sandwich ELSIA.Results Compared with control group,of lung tissues was observed in rats treated with OA induced ALI,which led PaO2 dropped,and lung tissue W/D ratio,PMN%in alvedolar lavage and IQA raised score in the lung at 2,4 or 6 hours after OA injection(P＜0.01).In addition,IL-6,IL-8,and IL-10significantly increased,IL-6[plasma,control:(73.95±14.68)pg/ml,2 h:(186.70±23.85)pg/ml,4 h:(238.50±26.46)pg/ml,6 h:(215.95±25.86)pg/ml,P＜0.01;lung tissue,control:(60.58±12.91)pg/ml,2 h:(160.32±24.57)pg/ml,4 h:(195.27±46.28)pg/ml,6 h:(185.66±17.42)pg/ml,P all =0.000)],IL-8[plasma,control:(80.69±20.42)pg/ml,2 h:(184.11±19.51)pg/ml,4 h:(286.20±53.34)pg/ml,6 h:(241.30±45.85)pg/ml,P＜0.01;lung tissue,control:(69.14±15.96)pg/ml,2 h:(174.10±20.36)pg/ml,4 h:(249.02±31.17)pg/ml,6 h:(237.74±34.18)pg/ml,P＜0.01] and IL-10[plasma,control:(39.78±8.97)pg/ml,2 h:(111.18±11.46)pg/ml,4 h:(115.60±13.91)pg/ml,6h:(102.41±9.93)pg/ml,P＜0.01;lung tissue,control:(71.86±14.19)pg/ml,2 h:(126.96±18.72)pg/ml,4 h:(151.88±27.61)pg/ml,6 h:(137.28±14.22)pg/ml,P all=0.000] levels.in association with a decreased H2S content of plasma lung tissue decreased in[plasma,control:(36.58±6.80)μmol/L,2 h:(21.30±2.75)μmol/L,4 h:(20.63±1.26)μmol/L,6 h:(20.00±1.60)μmol/L,P＜0.01;lung tissue,control:(27.61±2.20)μmol/L,2 h:(20.67±1.37)μmol/L,4 h:(20.79±1.10)μmol/L,6 h:(18.92±0.75)μmol/L,P＜0.01]were observed in the plasma and lung tissue of OA-treated rats compared to controls.Administration of NaHS prior to OA treatment could lessen the lung pathologic changes induced by OA and elevate the concentrations of H2S in plasma[4 h:(26.67±3.44)μmol/L vs(20.63±1.26)μmol/L,P=0.042;6 h:(26.98±4.93)μmol/L vs(20.00±1.60)μmol/L,P＜0.05]and lung tissue[4 h:(23.20±1.48)μmol/L vs(20.79±1.10)μmol/L,P=0.011;6 h:(21,43±1.79)μmol/L vs(18.92±0.75)μmol/L,P=0.016].At the same time,the levels of IL-6 in plasma(185.37±21.98)pg/ml vs(238.50±26.46)pg/ml,4 h,P=0.000;(124.22±21.84)pg/ml vs(215.95±25.86)pg/ml,6 h,P＜0.01]and IL-8(199.40±34.56)pg/ml vs(286.20±53.34)pg/ml,4 h,P＜0.01;(146.58±20.23)pg/ml vs(241.30±45.85)pg/ml,6 h,P＜0.01]decreased significantly,but the level of IL-10(154.48±18.08)pg/ml vs(115.60±13.91)pg/ml,4 h,P=0.000;(138.06±20.01)pg/ml vs(102.41±9.93)pg/ml,6 h,P＜0.01]increased significantly.Conclusions The levels of endogenous H2S drop during the course of ALI oleic acid induced in rats.Exogenous H2S could decrease the levels of inflammatory factors(IL-6and IL-8),but increase the level of anti-inflammatory factors(IL-10).It could change the ratio of inflammatory factors/anti-inflammatory factors and therefore play a protective role against oleic acid induced ALI in rats.