Effect of Ginsenoside Rb1 Preconditioning on the Expression of eNOS and NO of Myocardium during Ischemia/reperfusion Injury in Diabetic Rats

【摘要】：Objective:To investigate the effect of ginsenoside Rb1 preconditioning on endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) expression levels during myocardial ischemia and reperfusion in diabetic rats and establish a possible molecular mechanism. Methods:Male adult SD rats weighing 220～280g were used for this study. Type I diabetes mellitus was induced by intraperitoneal injection of streptozotocin (65mg·kg-1) and this was confirmed by fasting blood glucose ≥16.7mmol·L-1 (300mg·L-1). The animals were randomly divided into 5 groups:sham-operated (sham),ischemia/reperfusion (I/R),ginsenoside Rb1+I/R,L-NAME (a specific eNOS inhibitor) +I/R,and L-NAME+ginsenoside Rb1 group (L-NAME+Rb1). Ischemia/reperfusion was produced by occlusion of the anterior descending branch of left coronary artery (LAD) for 30 minutes and the occlusion of LAD was released to allow reperfusion for 120 minutes. In sham-operated group,LAD was exposed but not occluded. In groups L-NAME,L-NAME+Rb1 and L-NAME,10mg·kg-1 of L-NAME was injected into the femoral vein 25 minutes before initiation of occlusion. In groups Rb1 and L-NAME+Rb1,ginsenoside Rb1 40mg·kg-1 was administered intravenously vein 10 minutes before occlusion of LAD. In group sham-operated and group I/R,a mixture of balanced solution and polygeline (to the ratio of 3:1) was infused. Heart rate (HR) and mean arterial pressure (MAP) were recorded 10 minutes before ischemia (T1,baseline),after 15 minutes of ischemia(T2),and on the 30th minute,60th minute,and 120th minute (T3-T5) of reperfusion. The rate pressure product (RPP) was calculated as the product of the heart rate and the peak mean arterial pressure. The myocardial ischemia reperfusion injury was assessed by infarct size,plasma creatine kinase (CK),lactate dehydrogenase (LDH) and tissue histological changes. The extent of oxidative stress was determined by measuring plasma levels of malondialdehyde (MDA) and total superoxide dismutase (T-SOD). Expression of eNOS was determined by immunohistochemistry,and so was the concentration of myocardial NO. Results:Ginsenoside Rb1 preconditioning caused a smaller infarct size when compared with I/R group:36.90±2.34% versus 51.67±4.34% (P0.01). Lower plasma CK and LDH were found with the ginsenoside preconditioning. The myocardial oxidative stress and tissue histological damage was attenuated by ginsenoside Rb1 and also the expression of myocardial eNOS and NO were higher (P0.05). Conclusion:It can be concluded that ginsenoside Rb1 protected myocardium of the diabetic rat against ischemia/reperfusion injury via a mechanism related to the increase in the expression in the levels of eNOS and NO,and decrease in oxidative stress.