[Pathoanatomical and pathophysiological study of lung injury induced by activated complement in rat]

Acute lung injury induced by intravenous infusion of zymosan-activated plasma(ZAP) on Wistar rats was studied. A single infusion of ZAP resulted in an early occurrence of increased respiratory rate, decreased PaO2, elevated activity of superoxide dismutase(SOD) in the arterial blood and lung tissue. The results showed that the content of copperzinic superoxide dismutase(Cu Zn SOD) in bronchiolar columnar epithelial cells was elevated. Histological and electron microscopic examination showed that there was an accumulation of neutrophils in pulmonary microvessels and capillaries, endothelial cell and epithelial cell injury, and pulmonary edema etc. The tight junctions both in the epithelium and endothelium showed alterations in substructure including discontinuity, irregularity, free ends and distention of meshes as early as 2 to 4 h. In later stage, the severity of damage of tight junctions increased, while the number of strands in endothelial junctions reduced. All the parameters in the control group did not change significantly. From the results, the authors consider that acute lung injury is intimately related to the neutrophils and oxygen free radicals, the pathological basis of early pulmonary edema is alterations in the tight junctions of the alveolar epithelium and capillary endothelium.