Effects of ischemic time factors on reduction of myocardial ischemia-reperfusion injury by sulfentanil postconditioning in rats

Objective To evaluate the effects of ischemic time factors on reduction of myocardial ischemia-reperfusion injury by sulfentanil postconditioning in rats .Methods Healthy adult male Sprague-Dawley rats ,weighing 230-250 g ,were heparinized and anesthetized with intraperitoneal 5% chloral hydrate 8 ml/kg .The hearts were excised and perfused in a Langendorff apparatus with K-H solution .After 30 min of stabilization ,48 isolated rat hearts were randomly assigned into 6 groups （n=8 each） using a random number table .In I/R1-3 groups ,the hearts were subjected to 30 ,45 ,and 60 min of myocardial ischemia ,respectively ,followed by 90 min of reperfusion . In SP1-3 groups , the hearts were subjected to 30 , 45 , and 60 min of myocardial ischemia , respectively ,followed by 90 min of reperfusion ,and sulfentanil 100 nmol/L was added to K-H solution at 15 min of reperfusion for postconditioning . Left ventricular end-diastolic pressure （LVEDP ） , left ventricular developed pressure （LVDP） ,＋dp/dtmax ,-dp/dtmax ,HR and coronary flow （CF） were measured at the end of equilibration and 15 ,30 ,60 and 90 min of reperfusion .Creatine kinase （CK） and lactate dehydrogenase （LDH） activities in coronary effluent were measured at 5 min of reperfusion .Myocardial infarct size was determined in 5 hearts chosen＆nbsp;randomly at 90 min of reperfusion .Results LVEDP was significantly higher ,and LVDP , ± dp/dtmax and CF were lower at each time point of reperfusion than at the end of equilibration in I/R1-3 groups （ P0.05 ） .Conclusion Sulfentanil postconditioning can attenuate myocardial ischemia-reperfusion injury when the rats are subjected to 30 or 45 min of ischemia ,however ,it provides no myocardial protection when the rats are subjected to 60 min of ischemia . Key words: Time factors; Sulfentanil; Ischemic postconditioning; Myocardial reperfusion injury