ABSTRACT
<p><b>OBJECTIVE</b>To observe the ultrastructures of rat alveolar type II cells and change of composition of phospholipid(PL) and content of protein in pulmonary surfactant(PS), to investigate the relation between change in composition of PL and activity of alveolar type II cells.</p><p><b>METHODS</b>The rats lung injury models were made by intratracheally instilling bleomycin(BLM) (4 mg/ml, 5 mg/kg). 28 rats were divided into four groups: 3-day group, 7-day group, 14-day group and 28-day group. Preparations of each group were stained histochemically and examined by electron microscope, content of PL in BALF, composition of PL and content of protein of each group were determined respectively.</p><p><b>RESULTS</b>(1) Rats lungs in experimental groups were found that PS lost continuously, appeared homogenous and chorionic, dropped in the pulmonary alveolies. 3-day group was more apparent. Ruthenium red attaching on pulmonary surfactant was thicker in 3-day group, and the colour deeper, no difference in 7-day group and 14-day group, thinner in 28-day group. Content of PL in PS of BALF was increasing. 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. (2) Alveolar type II cells degenerated, necrotized, even disintegrated in 3-day group and 7-day group. 3-day group was more apparent. Proliferations of alveolar type II cells were found in each group, 7-day group was more apparent. We found that type II cells transformed to type I cells in 14-day group, extended and attached on bare basement membrane. Content of protein in PS was the highest in 3-day group, almost equal to the content of the control group in 28-day group.</p><p><b>CONCLUSION</b>Morphologic change and alternation of quality and quantity of PS after bleomycin-induced pulmonary injures specifically reflect the activity of alveolar type II cells. Measuring content of PL in BALF is one of simple and feasible method judging activity of alveolar type II cells when lungs of the rats are injured early by bleomycin.</p>