目的　探讨一氧化氮 (NO)对内毒素致伤大鼠急性肺损伤 (ALI)肺组织核因子 KB(NF kB)活性及肿瘤坏死因子 α(TNF α)水平的影响和防治ALI的作用机理。方法　观察内毒素(LPS)和LPS/NO对大鼠血氧分析和肺组织损伤的影响 ,并采用凝胶电泳迁移率改变 (EMSA)法检测肺组织核蛋白提取物中NF kB活性和检测的特异性及酶联免疫检测 (ELISA )测定肺组织匀浆TNF α含量改变。结果　NO吸入后 ,显著抑制LPS静注致大鼠急性肺损伤、肺组织核蛋白NF kB活性的增强以及肺组织匀浆TNF α含量的升高。结论　NO通过抑制NF kB活性 ,下调TNF α等炎症分子表达而发挥抗炎和防治ALI的作用。 Objective To investigate the effect of nitric oxide (NO) on nuclear factor kB (NF kB) activity and tumor necrosis factor α (TNF α) level in lungs of acute lung injury (ALI) induced by endotoxin in rats and its mechanism of action. Methods The effects of endotoxin (LPS) and lipopolysaccharide (LPS) on blood oxygenation and lung injury in rats were observed. The activity of NF kB in the nuclear extracts of lung tissue was detected by EMSA, Specificity and enzyme-linked immunosorbent assay (ELISA) determination of TNFα content in lung homogenate. Results NO inhaled significantly inhibited the acute lung injury induced by LPS, the increase of NF kB activity in lung tissue and the increase of TNFα in lung homogenate. Conclusion NO exerts anti-inflammatory and anti-ALI effects by inhibiting NF kB activity and down-regulating the expression of TNFα and other inflammatory molecules.