Brief femoral artery ischaemia provides protection against myocardial ischaemia-reperfusion injury in rats: the possible mechanisms

The present study was conducted to examine the role of nitric oxide (NO), mitochondrial ATP-sensitive K+ channels (mito K-ATP(+) channels) and reactive oxygen species (ROS) and their interdependence in brief femoral artery ischaemia-induced myocardial preconditioning. To assess myocardial injury, myocardial infarction was induced by occlusion followed by reperfusion of the left anterior descending (LAD) coronary artery in anaesthetized rats and was assessed by triphenyl tetrazolium chloride (TTC) staining. Left ventricular function was assessed by left ventricular end-diastolic pressure (LVEDP) and the maximal rate of rise of left ventricular pressure [LV(dP/dt)(max)]. Serumcreatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) were determined by colorimetric kits. Remote preconditioning (RPC) was induced by 15 min occlusion of femoral arteries followed by 10 min of reperfusion just before LAD coronary artery occlusion. Brief femoral artery ischaemia led to a 61% reduction in myocardial infarct size, 57% reduction in elevated serum LDH and 72% reduction in elevated CK-MB activities, and a significant improvement in LVEDP and LV(dP/dt)(max) compared with control animals. Pretreatment with 5-hydroxydecanoate (5-HD) or L-NAME or N-acetylcystein (NAC) blocked this protective effect of femoral artery ischaemia. Moreover, infusion of L-arginine or diazoxide before coronary artery occlusion markedly reduced the myocardial infarction and improved the left ventricular function. This effect of L-arginine was found to be abolished by the blockade of mito K-ATP(+) channels with 5-HD and, similarly, the effect of diazoxide was blocked in the presence of a ROS scavenger, NAC. The results suggest that brief femoral artery ischaemia-induced RPC is mediated by a combination of increased NO synthesis, opening of mito K-ATP(+) channels and increased ROS production. Moreover, it appears that NO is working upstream and acts via activation of mito K-ATP(+) channels, which subsequently increases the production of ROS.