| AIM: AT II is the stem cell of lung alveoloar epithelium, which is concerned with development and repair of injuries of lung. Many data show that AT II is associated with lung fibrosis, and makes an important role during lung fibrosis. Recently, especially in physiological and pathological status, the relation between AT II and non-respiratory function of lung has been paid attention to. The aim of this experiment is to investigate the change of morphological structure and proliferation activities during bleomycin-induced lung injury and to investigate the changing regularity of proliferation activities of AT II and the effect on repair function of injuried lung alveoloar epithelium by analyzing the quality and quantity of pulmonary surfactant after conducting bleomycin-induced lung fibrosis model and treating AT II cultivated in vitro to try to find out the basis for investigating status and role of AT II during lung fibrosis.METHODS: The lung injury models were made by intratracheal instilling of BLM(4mg.mr', Smg.kg"1). All rats were divided into four groups, 3-day group, 7-day group, 14-day group and 28-day group. Control groups were instilled with the same quantity of physiological saline water under the same condition. Lung preparations were stained histochemically with ruthenium red and examined by electron microscope. PL in PS of bronchoalveolar lavage fluid (BALF) were determined with High-performance liquid chromatographty (HPLC ) and spectrophotometry. Cell proliferation period of AT II cultivated in vitro treated bybleomycin was determined by flow cytometric analysis. Then the results were analyzed with compared method.RESULTS: (1) PS in control group was a continuous and homogenous electronic dense strip attaching on inner wall of lung alveoloar. The structure of AT II was intact and clear. Each experimental group was found that PS layer lost continuously, appeared homogenous and chorionic, dropping in the pulmonary alveolies, collecting into masses or scattering. The change in 3-day group was more apparent. Ruthenium red attaching on pulmonary surfactant was thicker and the colour deeper in 3-day group, no difference in 7-day group and 14-day group, thinner in 28-day group. Content of PL in PS of BALF was inclined to increase. Content of phosphatidylglycerol (PG) increased in 3-day group, decreased in 7-day, 14-day, and 28-day group. The change of content of phosphatidylinositol (PI) was reversed. The ratio of PG/PI increased in 3-day group, decreased in 7-day, 14-day, and 28-day group. The ratio of PG/PI decreased in 7-day, 14-day, and 28-day group after pharmic treatment. The results differed apparently compared with control group. (2) AT II cells degenarated, necrotized, even disintegrated, in 3-day and 7-day group the change in 3-day group was more apparent. The number of lamellar body in 3 days group decreased, appeared vacnolus partly or entirely. Lamella was irregular and thin, some dropping into T AT II .The number in 7-day group began to increase and become larger, apparently in 14-day and 28day group. Some of lamella were especially large. AT II proliferation could be seen in each experimental group, especially in 7-day group. (3) Basement membrane was in dropsy, denuded, even fragmentated in 3-day group and 7-day group. Inflammatory cells and fibroblasts in septum exudated into pulmonary alveolies. Broken basement membrane was embeded by extracellular matrix (ECM) and fibrinoid substance in 14-day group and 28-day group.lt was found that AT II cells transformed to AT I cells in 14-day group, extended gradually, attaching on bare basement membrane. (4) Content of protein in PS was highest in 3-day group, almost equal to content of control group in 28-day group. (5) Go/G, ratio of AT II after treating by bleomycin decreased the first day, began to increase the second day and was near to the level of control the eighth day. The number of dead cells(including apoptosis cells) increased the first day, reached the summit the second day, then decreased gradually, but did not reach the l...
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