Objective: To explore the effect of folic acid on lung ischemia-reperfusion injury in rats. Methods: Thirty healthy adult male SD rats were randomly divided into 5 groups with 6 rats in each group, of which 3 groups were gavaged with folic acid at doses of 5, 10, 20 mg/d for 1 week. Then, the folic acid groups and ischemia-referfusion group rats were constructed a model of lung ischemia-reperfusion, in which the left hilum was clamped for 30 min and reperfused for 2 h; sham operation group the left hilus was dissociated but not clamped. The pathological changes of lung tissue was observed by HE staining; the level of IL-8 and TNF-α were determined by ELISA. Results: Compared with the sham operation group, the lung injury severity  in the ischemia-reperfusion group was significantly serious (P<0.01); compared with the ischemia-reperfusion group, the severity in the three folic acid groups was significantly alleviated; compared with the 5 mg/d folic acid group, 10 mg/d and 20 mg/d folic acid groups had significantly less pathological lesions in the lung tissue(P<0.01), while there was no significant difference between the later two groups(P>0.05). Compared with the sham operation group, the level of IL-8 and TNF-α in the ischemia-reperfusion group and the folic acid groups was remarkably higher(P<0.01); compared with the ischemia-reperfusion group, the level of IL-8 and TNF-α in the three folic acid groups was markedly lower (P<0.01); compared with the 5 mg/d folic acid group, the level of TNF-α in 10 mg/d and 20 mg/d folic acid groups was greatly lower; while there was no significant difference between the later two groups(P>0.05); the decrease of IL-8 level in the three folic acid groups was in a dosedependent manner(P<0.05). Conclusion: Folic acid exerts protection on lung ischemia-reperfusion injury in rats.

［Key words］folic acid; lung ischemia-reperfusion injury; IL-8; TNF-α; rat