Protection Of Ischemia Preconditioning In Rat Lung From Ischemia-reperfusion Injury

It was initially thought that the lung was resistant to ischemic injury because of its dual pulmonary and bronchial arterial blood supply and its independent source of oxygen, available from the alveolar space. However, in the last 10 years, multiple studies have indicated that lung is one of preferred target organs of ischemia-reperfusion injury in many experimental studies and clinical conditions.Lung ischemia-reperfusion injury inevitably occurs within the first 72 hours after lung transplantation and is typically characterized by nonspecific alveolar damage, lung edema, and hypoxemia. The most severe form may not only lead to primary graft failure and remains a significant cause of morbidity and mortality, but also correlate with other complications after lung transplantation. It severely influences the survival and success of lung transplantation. Although the mechanism of lung ischemia-reperfusion injury remains not clear, many excited progresses have been made in prevention and therapy of lung ischemia-reperfusion injury and it has been proved that the new developed agents have a protective effect in ischemic-reperfusion injury such as nitric oxide, prostaglandins, complement inhibition, antagonist ofplatelet-activating factor and surfactant. All sorts of researches prompted that human lung protection from ischemia-reperfusion injury by heme oxygenase pathway, preconditioning and gene therapy might be three important measures in the future, then they would be the mostly directions of future studies.Tissues exposed to one insult can develop tolerance to a subsequent injury. This biological adaptation forms the basis of the concept of preconditioning. Various types of preconditioning have been used to protect the lung from ischemia-reperfusion injury. For instance, ischemic preconditioning, hyperthermic preconditioning, and chemical preconditioning have been shown to be successful in reducing lung injury in most cases. Ischemic preconditioning achieved by brief periods of ischemia and reperfusion before a prolonged period of ischemia was first described by Murry in the studies of protection of cardiac muscle in 1986, thereby human opened up the gate of endogenous protection of cardiac muscle. After this, most of the studies have shown ischemic preconditioning can relieve the injury from ischemoa-reperfusion in such solid organs as the kidney, the liver, and especially the heart. There were a few datum about lung ischemic preconditioning, so it is indispensable to explore the role of ischemic preconditioning in lung of ischemoa-reperfusion injury.To ivestigate the effects of ischaemia preconditioning on function of lung with ischaemia-reperfusion injury, we used rat model of single left lung of simulating transplantation in situ. 24 Wistar rats were divided randomly into 3 groups--Group I: control group, Group II: 10 min ischemic preconditioning group (10 min ischemia + 5 min perfusion),Group III: 5 min ischemic preconditioning group(5 min ischemia + 5 min perfusion). We applied two ischemic preconditioning in the experimental groups, and no ischemic preconditioning in the control group. After 1 h of normothermic ischemia, the lungs were reperfused for 30 min. Artery blood oxygen pressure (PaO2) were measured before ischemia and at the end of reperfusion respectively, while wet/dry ratio, counts of neutrophil, malondialdehyde (MDA) and supperoxide dismutase(SOD) levels in the lung tissue, lung parenchymal cell viability were determined at the end of reperfusion. Results: (l)There were no significant difference in PaO2 among the 3 group before ischaemia (P=0.16>0.05). (2) In the 10 min ischemic preconditioning group, PaO2, wet/dry ratio, counts of neutrophil, MDA and SOD levels in the tissue, lung parenchymal cell viability were not markedly different from CONT group (respectively P=0.28>0.05, P=0.79>0.05, P=0.73>0.05, P=0.29>0.05, P=0.58>0.05, P=0.29>0.05). (3) In the 5 min ischemic preconditioning group, PaO2, SOD levels in the tissue and lung parenchymal cell viability were predominant above CONT...