[Experimental study of dynamic changes in elastase-antiprotease in rabbits in the early stage of inhalation injury]

In this experiment, rabbit model with smoke inhalation injury was used. The study was designed to observe the dynamic changes of elastase activities of polymorphonuclear leukocytes (PMN), alveolar macrophages (AM) and bronchoalveolar lavage fluid (BALF); and trypsin inhibitory capacities of serum and BALF (STIC & BTIC). The relationships between these changes and acute lung injury, as well as the concomitant changes of arterial blood gas levels, lung water volume and pathomorphology of trachea and lung tissues were also observed. It was found that after injury the elastase activities of PMN and AM were markedly reduced, and the elastase activity of BALF was rapidly increased. STIC was also reduced. PaO2 progressively dropped and PaCO2 progressively increased. Animals showed respiratory distress. Pathomorphological phagocytes aggregations in lungs, pulmonary edema and pneumorrhagia were found. There were serious destructions of capillary endothelial cells, alveolar epithelial cells, basement membranes and interstitial fibers. The number of elastic fibers of parenchyma decreased. The lung water volume was markedly increased, and there was a significant correlation between the increment of extravascular lung water and the rising of elastase activity of BALF. On the basis of our observation, it is proposed that the imbalance of elastase-antiprotease may play an important role in the development of acute lung injury after smoke inhalation.