Experimental Research About Abnormal Mechanism Of Lung Water Metabolism In The Early Phase Of Lung Contusion

Objective To evaluate the roles of toll-like receptor-4,vascular endothelial cell growth factor and aquaporin-1 in the early phase of lung contusion related to the abnormal mechanism of lung water metabolism.Methods 30 healthy adult rabbits(weight about 2.5-2.8 Kg, female and male in half) were randomly divided into five groups: Control group (n=6), were only intubated through femoral artery for each rabbit; The other four groups called as lung contusion groups were divided according to the times (2h, 4h, 6h, and 8h later) after injury, and each group had 6 rabbits. The lung contusion groups were intubated through femoral artery, hit the right rabbit chest wall by a free-falling weight impacted device. Qualifications of hitting: Metal ball weight 0.352Kg, downcast height 1.55±0.13m, strike speed 5.58±0.22m/s. During the experiment, blood pressure, heart rate, respiratory rate, blood gas and other physiological parameters were monitored and calculated. X-RAY,CT were done after the trauma. The rabbits of control group were decapitated after at 8 hour point, The Lung contusion group were decapitated at different time points. Lung tissue samples were prepared in all groups. Microanatomy was examined,The water content of lung tissue was determined by measuring both wet and dry weight. Immunohistochemistry was used to investigated the VEGF expression, and the methods of RT-PCR were used to detect the expression for VEGF mRNA,TLR-4 mRNA,AQP-1 mRNA in the lung tissue at difference time courses. enzyme linked immunoabsorbed assay(ELISA) were dynamically observed the change in TNF-α,IL-6. The data was analyzed with statistical software of SPSS10.0, all measurement data expressed in: mean士standard deviation( x士s), the comparison among multiple exponent adopts one-way ANOVA, Pearson correlation analysis was to carried out between the different variances, the differential significance is judged by p<0.05.Results1. The early physiological changes after lung contusion include decreased of heart rate, increased of respiratory rate, decreased of blood pressure; the pathological changes of pulmonary tissue showed diffuse areas of intra alveolar hemorrhage with disruption of alveoli,interstitial edema,leukocyte infiltration in the alveolar spaces. Chest CT scan showed partial lamellar ambiguity shadow.2. The lung water content increased from 2 hours after lung contusion, showed predominance difference compared with the control group(p<0.01).3. The level of TNF-a,IL-6 were increased after lung contusion, showed predominance difference compared with the control group(p<0.01). The level of TNF-a elevated maximally at 4 hours after trauma.4. The TLR-4 expression in lung tissue was obviously up regulation after lung contusion, reaches the peak 6 hours after trauma; during 6-8 hours, the expression of VEGF was up regulation; the expression of AQP-1 was fall-off during the experiment.5. Relative correlation analysis among lung water content, the expression of VEGF mRNA, the expression of AQP-1mRNA: The level of VEGF mRNA and lung water content appeared positive correlation (r=0.66,p<0.01). The level of AQP-1mRNA and lung water content appeared negative correlation(r=-0.79,p<0.01).6. Relative correlation analysis among lung TNF-a and the expression of TLR-4mRNA: The level of TNF-a and TLR-4mRNA appeared positive correlation(r=0.46,p<0.05).Conclusions1. By hitting the right chest wall with a free-falling weight impacted device. Qualifications of hitting: Metal ball weight 0.352Kg, downcast height 1.55±0.13m, strike speed 5.58±0.22m/s. The animal model of isolated lung contusion could be stable established. 2. Compared with the control group, lung water content increased after lung contusion. That suggests in the early phase of lung contusion, the abnormal mechanism of lung water metabolism had happened.3. Relative correlation analysis among TNF-a and TLR-4mRNA expression: The level of TNF-a and TLR-4mRNA appeared positive correlation (r=0.46, p<0.01). That suggested after lung contusion, the more and more TNF-a up-regulation the expression of TLR-4.4. Relative correlation analysis among lung water content, the expression of VEGF mRNA, the expression of AQP-1mRNA: The level of VEGF mRNA and lung water content appeared positive correlation (r=0.66,p<0.01); The level of AQP-1mRNA and lung water content appeared negative correlation(r=-0.79,p<0.01). We can infer that VEGF and AQP-1 could probably participate in the abnormal mechanism of lung water metabolism in the early phase of lung contusion.