RESUMO
AIM: To explore the expressions and significance of angiopoietin-2 (Ang-2) and tyrosine kinase with immunoglobulin and epidermal growth factor homology domains-2 (Tie-2) receptors in a rat model of acute lung injury (ALI). METHODS: Wistar rats (n=42) were divided into control group (n=12) and cecal ligation and puncture (CLP) group (n=30). Control group underwent sham operation, and CLP group underwent cecal ligation and puncture to make the model of ALI. 12 h after sham operation or CLP, 6 rats in each group were killed, and arterial blood gas analysis and lung coefficient were tested. The expressions of Ang-2 and Tie-2 receptors in lung tissue were observed by immunohistochemical method. Blood samples of the rest rats were collected from vena caudalis, and Ang-2 levels were measured by enzyme linked immunosorbent assay (ELISA). The mortality rate in each group within 36 h was compared. The lung architecture was observed under microscope. RESULTS: The lung architecture in control group was clear and intact. Alveolar septum was thicker, blood capillary was congested, and neutrophils and macrophages were infiltrated in the lung tissue in CLP group. Tie-2 receptors were expressed in bronchial epithelial cells, smooth muscle cells and endothelial cells in control group. Besides the similar expression as control group, high expression of Tie-2 on neutrophils and macrophages in CLP group was observed. In the adhesion location of Tie-2 receptors positive inflammatory cells, there was stronger staining in endothelial cells. Ang-2 was expressed in smooth muscle cells, bronchial epithelial cells and endothelial cells in control group. The Ang-2 level in CLP group were higher than that in control group [(8.14±1.74) μg/L vs (4.63±0.49) μg/L, P<0.01], and the Ang-2 level of dead rats was higher than that of survival rats within 36 h in CLP group [(8.95±1.61)μg/L vs (6.80±0.96)μg/L, P<0.01]. Oxygen partial pressure in control group was lower (P<0.01) and lung coefficient was higher (P<0.01) than that in CLP group. CONCLUSION: Ang-2 and Tie-2 receptors may participate in the pathophysiology of ALI, and Ang-2 level is correlated with mortality.