Effects of preconditioning with leg ischemia on lung ischemia-reperfusion injury in rabbits

Objective To evaluate the effects of leg ischemic preconditioning on lung ischemia-reperfusion (I/R) injury in rabbits.Methods Eighteen healthy Japanese long-ear white rabbits of both sexes weighing 2.0-2.5 kg were randomly divided into 3 groups ( n = 6 each) : group I sham operation (group S) ; group II I/R and group ID leg ischemic preconditioning (group L) . The animals were anesthetized with iv barbital sodium (1 ml/kg) 25 g/L. Tracheal intubation was performed and the animals were mechanically ventilated. The left hilum of lung was threaded but no occlusion was performed and then the animals were observed for 340 min in group S. Left lung I/R was produced by left hilum of lung occlusion for 60 min followed by 180 min reperfusion in group I/R. Leg ischemia was induced by placing tourniquet on both legs. The animals underwent 3 episodes of 10 min leg ischemia at 10 min intervals, and 60 min later left hilum of lung was occluded for 60 min followed by 180 min reperfusion in group L. Blood samples from left internal carotid artery were taken for blood gas analysis before ischemia and at 15, 30, 60, 120 and 180 min of reperfusion. Respiratory index (RI) was calculated. The animals were killed at 180 min of reperfusion and the lungs were removed for determination of SOD and MPO activities, MDA content, calculation of W/D lung weight ratio, and lung permeability index (LPI) in broncho-alveolar lavage fluid (BALF), and histological examination with light microscrope, and diffuse alveolar damage (DAD) was scored. Results Compared with group S, RI, MDA content, MPO activity, W/D lung weight ratio, LPI in BALF and DAD scores were significantly increased while SOD activity decreased in group I/R ( P < 0.05 or 0.01). RI, MDA content,MPO activity, W/D lung weight ratio, LPI in BALF and DAD scores were significantly lower while SOD activity higher in group L than in group I/R (P < 0.05 or 0.01). There were no significant differences in the indices mentioned above between group L and S. The histological damages were significantly milder in group S and L than in group I/R.ConclusionLeg ischemic preconditioning can attenuate the lung I/R injury in rabbits. Key words: Lower extremity;  Ischemic preconditioning;  Lung;  Reperfusion injury