| Objectives: To explore the protection effect and mechanism oflung ischemic preconditioning on lung and myocardium in caninecardiopulmonary bypass(CPB). Methods:12 adult mongrel canines (12～15 kg) were randomlydivided into two groups, 6 for Control group(Group C), in which theCPB was established by abdominal aorta and right atrium cannulation,Experimental group was treated with ischemic preconditioning, inwhich left lung hilus were clamped for two cycles of five minutesfollowed five minutes released before cross-clamping of the aorta in sixcanines(Group IP). The technique of myocardium protection and cardiacarrest was the same in both groups(cold crystalline cardioplegia). CPBwas controlled running for 1 hour in both groups. The lung andmyocardial tissue were sampled at the time of pre- CPB and 120minutes after reperfusion to test the wet/dry ratio of lung tissue andmyocardial water content(MWC), maleic dialdehyde(MDA )andsuperoxid dismutase(SOD) of both tissue. Lung and myocardial biopsieswere obtained before and after CPB in both groups for microscopepathological examination. Results: 1. After reperfusion, The wet/dry ratio of lung tissue inGroup IP was significantly lower than that in Group C(3.4867±0.6776 vs5.3067±0.3034,P<0.05). However, they were significantly higher thanthat before CPB in both group(which vs 2.4183±0.3198 and2.795±0.4667,P<0.01); The MDA of lung tissue in Group IP wassignificantly lower than that in Group C(5.3517±1.0769 vs7.4002±1.1569nmol/mgprot, P<0.05). However, they weresignificantly higher than that before CPB in both group(which vs3.3321±1.0475 and 2.7083±0.5206nmol/mgprot,P<0.01); SOD activityof lung tissue in Group IP was significantly higher than Group C(127.4512±18.88 vs 103.6103±9.5299 U/mgprot,P﹤0.05). However,they were significantly lower than that before CPB in both group(whichvs 169.6503±15.5514 and 157.8102±13.3192 U/mgprot,P<0.01) . 2. After reperfusion, the MWC of myocardium in Group IP wassignificantly lower than that in Group C(64.6173±4.1682 vs77.3333±3.0807,P<0.05) . However, they were significantly higher thanthat before CPB in both group(which vs 46.8171±4.5727 and48.0333±5.0015, P<0.01 ); The MDA of myocardium in Group IP wassignificantly lower than that in Group C(5.3233±1.5304 vs7.5517±1.0236 nmol/mgprot, P<0.05). However, they weresignificantly higher than that before CPB in both group(which vs2.7067±0.3479 and 3.0433±0.3024,P<0.01); SOD activity ofmyocardium in Group IP was significantly higher than Group C(166.0104±6.3458 vs 140.4514±13.9413 U/mgprot,P<0.05). However,they were significantly lower than that before CPB in both group(whichvs 195.3621±11.3572 and 199.5621±10.3322 U/mgprot,P<0.01) . 3. pathological examination of lung and myocardial tissue revealedthat in Control group there were more obvious intraalveolar hemorrhage,leukocyte adherence and interstitial edema compared with group IP. Conclusion: The study indicates that lung ischemic preconditioningmay have protective effect on lung and myocardium after CPB. Thepossible mechanism was that ischemic preconditioning reduced theproduction of ischemia-reperfusion injury. |
