| Background: The reperfusion therapy following acute myocardial infarction may cause myocardial ischemia-reperfusion injury. Ischemia postconditioning is an effective way to alleviate myocardial ischemia-reperfusion injury. Certain medication can exert protective function which calls pharmacological postconditioning through simulative endogenous protective mechanism after ischemia and before reperfusion. Pharmacological postconditioning has similarly protective mechanism with ischemia postconditioning. However, recently research found that diabetes or hyperglycemia may weaken ischemia or pharmacological postconditioning's protection on myocardium, which greatly restrict the clinical application of ischemia postconditioning and pharmacological postconditioning.Objective: The present study was designed to investigate: (1)to build up a myocardial ischemia-reperfusion model on type 2 diabetic rats which closer to clinical practice; (2) whether rosuvastatin postconditioning combined with ischemia postconditioning alleviates myocardial ischemia-reperfusion injury on type 2 diabetic rats, and possible mechanism.Methods: (1)Wistar rats were randomly allocated into two groups (n=24): Sham treated intraperitoneal injection of 10% NA (230mg/kg), after 15mins, following with intravenous injection of citrate buffer (6.5ml/kg); Type 2 diabetic group treated intraperitoneal injection of 10% NA (230mg/kg), after 15mins, following with caudal vein injection of 1% STZ(65mg/kg). Feed rats with normal diet after injection, monitoring their weight and fasting plasma glucose (FPG). Nine weeks later, in anesthetized open-chest type 2 diabetic rats, the left main coronary artery (LCA) was occluded for 30mins followed by reperfusion (R) for 120mins. All rats were randomly divided into two groups including: Sham threading without occluding; Control without other interventions. Triglyceride(TG) and total cholesterol were evaluated by automatic biochemical analyzer, infarct size by TTC, ultrastructure by electron microscope. (2) Type 2 diabetic Wistar rats, whose LCAs were occluded for 30mins followed by sustained relaxation for 120mins, were randomly allocated into six groups(n=10); Sham threaded without occluding; Control without other interventions; Ischemic postconditioning(Post) treated three times of 10s R and 10s I before R; Rosuvastatin Postconditioning(RSV) pushed rosuvastatin 5mg/kg in external jugular vein slowly 3mins before R; RSV+Post; RSV+Post+LY294002 with an additional injection of PI3-K inhibitor LY294002 0.3mg/kg in external jugular vein slowly 15mins before R. Infarct size was evaluated by TTC, ultrastructure by electron microscope, expression of phosphorylate AKT, total AKT, phosphorylate eNOS, and total eNOS by Western-blot.Results: (1) Compared with normal group, type 2 diabetic group had higher TG in blood (1.46±0.19mmol/L vs. 0.73±0.11mmol/L, p<0.05), higher cholesterol (1.93±0.12mmol/L vs. 1.51±0.10mmol/L, p<0.05), clearly higher FPG (148.05±4.13 mg/dl vs. 117.04±2.87 mg/dl, p<0.05) without less reduction in weight (320.22±9.11g vs. 319.83±9.00g,p=0.88). Compared with Sham(type 2 diabetic), Control(type 2 diabetic) had higher mitochondria score (3.51±0.23 vs. 0.00±0.00, p<0.01), larger myocardial infarct size {(70±5)% vs. (0±0)%, p<0.01}. (2) Compared with Control, RSV,Post,RSV+Post could activate PI3K route which up-regulated expression of phosphorylate AKT and eNOS (p<0.05), alleviate myocardio ultrastructure injury, and reduce myocardial infarct size. Compared with RSV and Post, RSV+Post could futher activate PI3K route which reduce higher expression of phosphorylate AKT and eNOS (p<0.05), alleviate myocardio ultrastructure injury (1.15±0.32 vs. 2.42±0.22,2.35±0.25, p<0.01), and reduce myocardial infarct size {(33±2)% vs. (46±2)%,(48±2)%, p<0.05}. However, PI3K inhibiter LY294002 could completely block the PI3K-AKT-eNOS signaling pathway in RSV+Post, and abrogate the RSV+Post-induced cardioprotection.Conclusions: (1) Build up a myocardial ischemia-reperfusion model on type 2 diabetic rats successfully through intraperitoneal injecting nicotinamide (NA) united Intravenous injection of streptozotocin (STZ) and ligating in situ left coronary artery nine weeks later, which provides a reliable animal model for pathophysiological mechanisms research and prevention and control measures in myocardial ischemia-reperfusion injury on basic of type 2 diabetic. (2) Probably through enhancing the activation of PI3K-AKT-eNOS signaling pathway, the combination of rosuvastain and ischemic postconditioning enhance its protective effects on merely Post or RSV's cardioprotection for ischaemia-reperfusion injury on type 2 diabetic rats.
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