Abstract: 【Objective】 To discuss the significance of porcine pulmonary surfactant protein A (SP-A) in acute lung injury (ALI) and in veterinary clinical diagnoses and cure porcine respiratory disease (PRD), diversification of SP-A concentration in porcine serum and branchoalveolar lavage fluid (BALF), and relationship between the SP-A concentration and the changes of lung water content, which is the index of the severity of lung injury, was assessed. 【Method】 Eighteen healthy Large White piglets of 50±1 days were collected to establish a model of oleic acid (OA)-ALI containing normal saline (NS) group and OA group. At 1, 3, 6 h time point, the SP-A concentration in serum was measured by ELISA technology, and the SP-A concentration in BALF was measured by Western blotting technology, respectively. Also, the correlation between the SP-A concentration in serum and the lung water content, and between the SP-A concentration in BALF and the lung water content were studied by Kendall correlation analysis. 【Result】Compared with the NS group, porcine lung water content of OA group was significantly increased at 1, 6 h time point (P＜0.05), and was extremely significantly increased at 3 h time point. In OA group (P＜0.01), porcine lung water content at 3 h time point was higher than those at 1 h time point, and porcine lung water content at 6 h time point was lower than those at 3 h time point, but both of the difference was not significant. It was deduced that the 1 h time point fell into protophase of lung injury, lung injury was more severe at 3 h time point, and 6 h time point fell into paracmasis of lung injury. Compared with the NS group, the SP-A concentration in serum of OA group was extremely significantly increased in protophase of lung injury (P＜0.01), and that of OA group was higher than those of NS group in severe period and protophase of lung injury, but both of the difference wasn’t prominent. Moreover, the SP-A concentration in serum of OA group in severe period was extremely significantly reduced compared with those in protophase of lung injury (P＜0.01), and the SP-A concentration in serum of OA group in paracmasis was significantly reduced compared with those in severe period of lung injury (P＜0.05). During different periods of lung injury, the SP-A concentration in BALF of OA group was extremely significantly reduced compared with the NS group (P＜0.01). Moreover, the SP-A concentration in BALF of OA group in severe period was extremely significantly reduced compared with those in protophase of lung injury (P＜0.01), and the SP-A concentration in BALF of OA group in paracmasis was extremely significantly increased compared with those in severe period of lung injury (P＜0.01). Correlation analytic results showed that there was an extremely significantly positive correlation between lung water content and ELISA assaying for SP-A concentration in serum (r=0.50327, P＜0.01), and there was extremely significantly negative correlation between lung water content and Western blotting assaying for SP-A concentration in BALF (r=-0.72499, P＜0.0001). 【Conclusion】 As the expression of SP-A is not pulmonary tissue specific, there are still some further investigations left that porcine SP-A concentration in serum is taken as a marker for evaluation of the severity of lung injury. Porcine SP-A concentration in BALF could be taken as an index for evaluation of the severity and prognosis of lung injury during ALI. This research has established a primary foundation for clinical diagnoses and cure of PRD, and development of related research through assay for SP-A concentration in porcine serum and BALF.

Key words: surfactant associated protein A, acute lung injury, serum, branchoalveolar lavage fluid, ELISA, western blotting