Roles of reactive oxygen species in the reduction of myocardial ischemia-reperfusion injury by fentanyl postconditioning and remote limb ischemic postconditioning in rats

Objective To investigate the role of reactive oxygen species (ROS) in the reduction of myocardial ischemia-reperfusion (I/R) injury by fentanyl postconditioning and remote limb ischemic postconditioning in rats.Methods Sixty-three male Sprague-Dawley rats,aged 8 weeks,weighing 250-350 g,were equally and randomly allocated into 7 groups:sham operation group (group S),group I/R,fentanyl postconditioning group (group F),remote limb ischemic postconditioning group (group R),ROS scavenger N-(2-Mercaptopropionyl) glycine (MPG) group (group M),MPG + fentanyl postconditioning group (group MF),and MPG + remote limb ischemic postconditioning group (group MR).Myocardial I/R was induced by occlusion of anterior descending branch of left coronary artery for 30 min followed by 180 min of reperfusion.In group S the anterior descending branch was only exposed but not ligated.MPG 5 mg/kg was infused intravenously from 5 min before ischemia to 15 min of reperfusion in groups M,MF and MR,while the equal volume of normal saline was given in the other four groups.In groups F and MF,fentanyl 30 μg/kg was injected intravenously at 15 min of myocardial ischemia.In groups R and MR,the animals underwent 10 min ischemia of bilateral hind limbs starting from 15 min of myocardial ischemia.Arterial blood samples were taken at 180 min of reperfusion to determine the serum cardiac troponin I (cTnI) concentration.The rats were then sacrificed.The infarct size was measured by TTC.Results Compared with group S,the serum cTnI concentration and infarct size were significantly increased in the other six groups (P ＜0.05).Compared with group I/R,no significant change was found in the serum cTnI concentration and infarct size in M group,and the serum cTnI concentration and infarct size were significantly decreased in F and R groups (P ＜ 0.05).There was no significant difference in the serum cTnI concentration and infarct size between MF group and F group (P ＞ 0.05).The serum cTnI concentration was significantly higher and the infarct size was larger in group MR than in group R (P ＜ 0.05).Conclusion ROS is involved in the reduction of myocardial I/R injury by remote limb ischemic postconditioning in rats,but not in the myocardial protection provided by fentanyl postconditioning. Key words: Reactive oxygen species;  Fentanyl ;  Lower extremity ;  Myocardial reperfusion injury; Ischemic postconditioning