The Effects Of Exogenous Pulmonary Surfactant And Ambroxol On Pseudomonas Aeruginosa Pneumonia In Rats

【Objective】Pseudomonas aeruginosa (PA) is one of the most important pathogens in hospital acquired infection. PA pneumonia is associated with high mortality, especially in its severe form which caused by the muti-drug resistant strain. The focus of research has always been on a therapy that would reverse the body's apophylaxis and to improve the effectiveness of antibiotics. Some research work showed that both the phospholipid and the associated protein subunit of pulmonary surfactant (PS) could inhibit many species of virus and bacteria. The aim is to study the effect of PA induced pneumonia in rats on endogenous PS components of the alveoli and to evaluate the effect of exogenous PS replacement therapy on those rats. It is also to evaluate the effect of ambroxol, an agent that promotes the production and release of endogenous PS, on PA induced pneumonia in rats and the ultrastructural changes in the rats' pulmonary surfactant system. 【Methods】Animal models of rats with PA pneumonia were obtained by injecting 0.2ml of P. aeruginosa (ATCC27853, 6×108 CFU/ml) intratracheally. Eighty-four SD male rats were randomized into 5 groups: (1) Group PS (15 rats) - exogenous PS (50mg/kg) was injected intratracheally into their lungs after 6hrs of PA challenge; (2) Group AM (18 rats) - Ambroxol (MucosolvanR), (20mg/kg, iv) was administered after 6hrs of PA challenge; (3) Group NS (18 rats) -the same amount of Normal Saline (1.25ml/kg) was injected intratracheally into their lungs after 6hrs of PA challenge as control; (4) Group NAM (15 rats) - Normal rats were injected with Ambroxol intrvenously as in the test group; (5) Group NOR (18 rats) - Normal rats were injected with normal saline intratracheally in a similar pattern. Six hours after the above procedure, the wet/dry ratio (W/D) of theleft lung tissue was measured in 5 rats from each of the five groups. Histopathologic changes in the lung tissues were observed in the right lungs. The number of polymorphonuclear(PMN) leukocytes infiltration into the lung tissue was calculated by half-quantitative analysis in high power field(×400). Bronchoalveolar lavage (BAL) was performed with normal saline (at 37℃ and at a total dose of 40ml/kg) for each of the 10 rats from all the groups. The volume of fluid to be instilled was divided in a ratio of 4: 3: 3 and the amount of fluid recovered from the lung was approximated to the highest possible lavage fluid recovery rate for examination. Concentrations of total proteins (TP), by Lowry's method, total phospholipid (TPL), by Bartlett's, and dipalmitoylphosphatidylcholine(DPPC), by Mason's, were analyzed in the bronchial alveolar lavage fluid (BALF). The ratios DPPC/TPL and DPPC/TP were computed. Bacterial culture of BALF was carried out and their colonies were counted. Ultrastructural changes were observed by electron microscopy in the PS layer of the alveolar surface which showed changes in the lamellar bodies of the type II alveolar epithelium in 3 rats of each of Groups AM, NAM and NOR. Both Anova and T-Test were employed accordingly for all statistical analysis.【Results】 ① Macropathologically, the lungs increased in weight and size in all of the PA-challenged rats more than in normal ones. The surfaces of the lungs were rough with some purulent spots or pustules whose diameters were about 1-3mm. A flow of pink fluid was observed on the cut cross-sectional surface of the lung when it was squeezed. The pulmonary pathologic changes showed a decreasing trend of severity from Groups NS to AM with Group PS having the mildest. While Group NAM showed no pathological changes. The W/D ratio revealed statistically significant increase among Groups PS (5.77±0.46), AM (7.47±0.22), and more especially Group NS (8.58±0.39). Group PS compared with Group NS gave a P<0.05 whereas Group AM compared with Group NS had P>0.05. ②Pulmonary pathologic study revealed striking contrasts between therapeutic groups and the control group. In Group NS, there was bronchialmucosal epithelial cell...