The Effects Of Hyperbaric Oxygen Combined With Ischemic Preconditioning On Ischemia And Reperfusion Injury Of Heart Of Rabbits

Objective To evaluate the effects and mechanism of hyperbaric oxygen (HBO) combined with ischemic preconditioning (IP) on ischemia and reperfusion injury of heart of rabbits.Methods 88 family rabbits were allocated to one of five groups randomly: pseudo-operation group (group P), ischemia and reperfusion group (group IR), schemic preconditioning group (group IP), hyperbaric oxygen infusion group (group HBO), hyperbaric oxygen infusion combined with ischemic preconditioning group (HBO+IP), underwent general anesthesia and mechanical ventilation, the hearts were exposed via left parastemectomy.All the rabbits in group IR, IP,HBO and HBO+IP received a 60-minute ischemia and 120-minute reperfusion by LDA occlusion and release, whereas those in group IP and HBO+IP received three cycles of 5 minutes ischemia and 5 minutes reperfusion by LDA occlusion and release before long time LDA ligation.HBO solution was infused via venous to the rabbits in group HBO and HBO+IP during long time ischemia and reperfusion, Saline was infused to rabbits in other groups at the same rate.At the time of O minute of long time ischemia, 60minutes and 120 minutes reperfusion, Some rabbits in group IR, IP,HBO and HBO+IP were killed, and the area at risk (AAR, blue-dye negative) of left ventricle were delinated,little parts of AAR of left ventricle were stored in liquid nitrogen.The left parts of AAR of left ventricle at 120 minutes reperfusion were cut into slices and incubated in triphenyltetrazolium chloride (TTC, Sigma),slices were weighed and infarct size was caculatedo The activity of superioxide dismutase (SOD) and the quantity of malondialdyde (MDA) of myocardium was detectedo The expression of myocardial ICAM-1, Heat Shock Protein 70 (HSP70) was detected by immunohistochemistry methods. And the expression of Nuclear Factor-κB (NF-κB) was detected by Western blot. Microstructure of myocardial was studied under electronic microscope oResult The infarct size of area at risk (AAR) in Group HBO+IP is 18.5±3.5%, significantly reduced than those in group IR 45.5±4.3 %and IP 25.24±4.2% and HBO 26.44±3.1% respectively.The activity of SOD in other groups was reduced significantly compared with that in group P, and also reduced significantly in group IR compared with those in group IP, HBO and HBO+IP respectively. The quantity of MDA in myocyte changed reversely.ICAM-1 and HSP 70 expressed in all groups, ICAM-1 expression in group HBO+IP, group HBO and group IP was significantly down-regulated than that in group IR respectively; HSP 70 expression in group HBO+IP was also up-regulated significantly at 120min time point than that in group IR; The expression of NF-κB was down-regulated partially after reperfusion in group HBO+IP and IP and significantly up-regulated in group IR after reperfusion.The myocyte microstructure of group HBO+IP changed least compared with that in group IR, with less tissue edema and less swelling of mitochondria.Conclusion HBO combined with IP ,HBO could significantly reduce infarct size of AAR of family rabbits.The possible mechanism might be below: HBO combined IP could protect the activity of SOD, regulate the expression of NF-κB, then down-regulate the expression of ICAM-1 and up-regulate the expression of HSP 70 respectively.The myocyte protective mechanism of HBO combined with IP might also including the osomosis of HBO reducing the eadema of myocyte caused by hypoxemia; Reduce the production of MDA, Minimize the damage to the microstructure of myocyte, especially to mitochondria.