[An aspiration pneumonia in acute airway damage model induced by HCl and/or LPS]

The purpose of this study is to evaluate chemical and pathological changes of the lung and to elucidate the role of TNF alpha and elastase in acute lung injury induced by HCl or lipopolysaccharide (LPS). Anesthetized rats were injected with pH 1.4 0.7 ml/kg body weight of HCl and 0.5 mg/kg body weight (BW) of LPS (E. coli) into the lung. Acute tracheal injury model (Mendelson Syndrome) were made. Control animals received only saline. Animals were sacrificed 1, 6, or 12 hours after the HCl or LPS or HCl and LPS injection, bronchoalveolar-lavage (BAL) was performed in the same way in control and experimental groups. The other animals which were treated as well were excised by histology. There was neither increase in TNF alpha-production nor increase in neutrophils resulting from HCl injection only. Elastase-like activity was not detected in animals treated only with HCl. However, 1 hour after LPS injection, the production of TNF alpha (37.0 +/- 8.0 Units/ml) was significantly greater than that of the control group (12.1 +/- 4.2 Units/ml) in BALF. Six hours after HCl and LPS injection, the concentration of elastase-like activity (0.023 +/- 0.002 nM) was significantly greater than that of the LPS group (0.011 +/- 0.001 nM). Only patches of intraalveolar hemorrhage and elevation of fibrin was observed in the HCl injected rats at 1 hour after injection. Six hours after LPS injection, the alveolar spaces were filled with large amounts of neutrophils. These findings suggest that TNF alpha and elastase play a significant role in HCl and LPS-induced acute lung injury.