Protective Effect Of Ischemic Postconditioning On Ischemia-reperfusion Injury Of Lung

Objective Lung ischemia-reperfusion injury is a major cause for respiratory dysfunction, even failure after cardio-pulmonary bypass and Transplant of lung. Ischemic postconditioning provide a protective effect on ischemia-reperfusion injury of heart and lung. Our experiment to investigate the protective effect of ischemic postconditioning on lung ischemia-reperfusion injury of rats and possible mechanism . It will clinically supply theoretical base on lung reflowing after blood flow occlusion.Material and Methods Animals were anesthetized by sodium pentobarbital (30mg/kg). They were connected to little animal ventilator after resection of trachea. Respiratory rate: 60bpm, Work pressure (tidal volume): 0.02MP, I:E: 1:1.5. Experimental rat model of acute lung ischemia- reperfusion was established by occluding left lung hilum, 24 healthy female Sprague-dawley rats, weighing 280-320g, were randomly divided into 3 groups(eight in each group): (1) sham-operated group(SO): Hilum of left lung was just separated after entry into the thorax, blood flow of left lungs was not blocked. The left lung was subjected to 105 min of continuous reperfusion. (2) ischemia-reperfusion group (IR) : The left lung were undergone 45 min of the lung hilum occlusion followed by 60 min reperfusion (3) ischemic postconditioning group(IPC): after 45 min of left lung hilum occlusion, reperfusion was initiated for 1 min followed by 1 min of reocclusion, repeated for five cycles. IPC was established by several brief reperfusion-ischemia before continuous reperfusion .The concentration of malondialdehyde (MDA) and the activity of superoxide dismute (SOD) and myeloperoxidase(MPO), wet to dry weight ratio(W/ D )in the lung tissue were determined respectively. Pathological changes of the lung tissue were also observed. All data were expressed as mean±SD. Comparisons between groups were analyzed with one-way ANOVA test. P values less than 0.05were statistically considered significant.Results 1. The concentration of MDA and activity of MPO in the lung tissue was significantly elevated after 60min reperfusion in IR groups against SO group (PO.01), while the activity of SOD was significantly reduced (P<0.01). Compared with IR group, the concentration of MDA(P<0.05) and activity of MPO (PO.Ol)in IPC group was markedly reduced, while the activity of SOD was significantly increased (PO.05) . 2.The ratio of W/D in the lung tissue was significantly increased in IR group against SO group(P<0.01), while The ratio of W/D was markedly reduced in IPC group against IR group. 3. Lung tissue congestion and foam-like secretion occurred in lung and trachea in IR group after 60 min reperfusion. Under light microscope, tissue structure was clear and alveolar wall was thin in SO group, while alveolus interval widen and edema obvious in IR group The observe of pathomorphology of lung tissue in IPC group showed inflammatory cells infiltration and edema in the pulmonary alveolus interval, the infiltration of erythrocyte, inflammatory cell and serosity in the alveolus were significantly lighter than IR group.Conclusion 1. IPC can be able to relieve the increase in permeability of lung capillary. 2. IPC may lessen the infiltration of PMN in the ischemic lung tissue. 3. IPC may inhibit the excessive product of oxygen-derived free radicals after reperfusion, 4. Ischemic postconditioning can play a protective role on lung reperfusion injury.