Role of nitric oxide in lung injury.

(1)将1 mg/kg体重的内毒素注入大鼠右心室。术后6、12、24、48小时肺组织病理示间质单核细胞浸润，肺泡水肿。6小时后肺匀浆免疫印迹（WB）显示诱导型一氧化氮合酶（iNOS）蛋白表达。(2)肺组织免疫染色显示60 ~ 70%肺泡II型细胞和少量肺泡巨噬细胞表达iNOS蛋白。全肺和离体II型细胞的WB均显示130 kD的iNOS条带。未处理组肺无iNOS蛋白表达。(3) RT-PCR观察全肺和离体II型细胞360 bps iNOS mRNA的表达。II型细胞的原位杂交显示iNOS mRNA的反义核糖探针阳性信号。无iNOS mRNA核探针检测信号，提示该过程具有特异性。(4)采用免疫组织染色法测定内毒素前12小时腹腔注射地塞米松（4mg/kg wt）对肺组织iNOS蛋白表达的影响。地塞米松组ⅱ型细胞iNOS蛋白表达受到抑制。地塞米松还能抑制离体II型细胞iNOS蛋白的表达。(5)综上所述，在体内内毒素诱导的肺损伤中，肺泡II型细胞存在iNOS蛋白的表达，其表达在转录阶段受到调控，地塞米松抑制iNOS的表达。

(1) We administered endotoxin of 1 mg/kg body weight into the right ventricle in rats. Histopathology of the lungs showed mononuclear cell infiltration in the interstitium and alveolar edema 6, 12, 24 and 48 hour later. Western blotting (WB) of lung homogenate of 6 hour later revealed expression of inducible nitric oxide synthase (iNOS) protein.(2) Immuno-histological stain of the lung showed expression of iNOS protein on 60 to 70% of alveolar type II cells and on a small number of alveolar macrophages. WB of both the whole lung and isolated type II cells showed iNOS band of 130 kD.There was no expression of iNOS protein in untreated lungs.(3) Expression of iNOS mRNA of 360 bps was observed on RT-PCR for the whole lung and isolated type II cells. In situ hybridization for type II cells revealed a positive signal to anti-sence riboprobe for iNOS mRNA.There were no signals to sence riboprobe for iNOS mRNA, indicating specificity of the process.(4) We determined the effect of intra-peritoneal administration of dexamethasone (4mg/kg wt) 12 hour before endotoxin on expression of iNOS protein in the lung by immuno-histological stain. Expression of iNOS protein on type II cells was suppressed in dexamethasone-treated lungs. Dexamethasone also inhibited expression of iNOS protein on isolated type II cells.(5) In summary, there was expression of iNOS protein on alveolar type II cells in in vivo endotoxin-induced lung injury, which was regulated at the transcription phase, and dexamethasone inhibited the iNOS expression.