The Protective Effect Of Radix Morindae Officinalls On Myocardial Ischemia Reperfusion Injury In Rats

Preconditioning the heart with a brief period of ischemia followed by reperfusion renders it very resistant to injury from a subsequent prolonged ischemia. The protection by preconditioning mainly lies in limiting infarct size, reducing the incidence of ventricular arrhythmia and improving postischemic cardiac function. Pharmacological preconditioning protection against heart injury is trigged by medicines which can mimic beneficial effects of cardiac ischemic preconditioning. That would be helpful to probe the mechanism of IPC and develop novel access to treatment of the cardiovascular diseases. There are two main hypotheses, namely oxidative stress and Ca2+-overload, which have been proposed to explain the pathogenesis of ischemia-reperfusion injury. Oxidative stress is usually associated with increased formation of reactive oxygen species(ROS), which may result in a depression in the sarcolemmal Ca2+-pump ATPase and Na+-K+-ATPase activities; these changes lead to decrease Ca2+-efflux and to increase Ca2+-influx respectively. ROS can also depress the sarcoplasmic reticulum Ca2+-pump ATPase and thus inhibit Ca2+ sequestration from the cytoplasm in cardiomyocytes. The depression in Ca 2+-regulatory mechanism by ROS ultimately results in intracellar Ca2+ overload. All endogenous antioxidants may act in concert to inhibit or delay the oxidative damage to subcellular proteins, carbohydrates, lipids and DNA. Endogenous nitric oxide(NO) has been reported to play an important role in late preconditioning, that is to say, it serves both as a trigger and a mediator. Two different NOS isforms are sequentially involved in the pathophysiologic cascade of late preconditioning, with eNOSgenerating the NO which acts as a trigger, and iNOS then generating the NO which acts as a mediator which protects against ischemia. Recently, there has been great development in Chinese medicine to protect myocardium against ischemia reperfusion injury. Di-ao-xin-xue-kang (DK), an effective Chineses medicine has been being used in clinical treatment of myocardial ischemic disease. The extract of Radix moridae officinalls (RMO) has been reported to increase antioxidants in brain and liver but there's had no report in heart. We preconditioned rat hearts with aqueous extract of RMO and with DK as positive control drug to investigate the effect of RMO on myocardial ischemia reperfusion injury.Methods: Three different concentrations of aqueous extract of RMO: 0.45g/ml, 0.15g/ml and 0.05g/ml were prepared and DK Capsule inclusion was mixed with 0.5% sodium carboxymethyl cellulose into suspension with the concentration of 7mg/ml. 96 Wistar rats (half in male and female) were randomly divided into 6 groups, namely sham operation (Sham) group, myocardial ischemia/reperfusion (I/R) model group, positive control drug: DK group, and three different doses of RMO: 4.5g/kg, 1.5g/kg, 0.5g/kg groups. The rats in DK and three different doses of RMO groups were infused intragastricly with the DK suspension 0.7g/(kg-d) and the three concentration of RMO 4.5g/ (kg-d), 1.5g/ (kg-d), 0.5g/ (kg-d) accordingly for 10 days, while the same volume of deionized water infused intragastricly in Sham and I/R model groups. After 24 hours of the last intragastric infusion, all rats were subjected to openning chest then the left anterior desending coronary arteries (LAD) were ligated for 30min and undamped for 90min except the rats with only thread-drawing in Sham group. Hemodynamics, ischemic zone size and infarct size (IZS and IS) of myocardium and scores of ventricular arrhythmia were measured. One half rats of every group were injected Evans blue then the hearts were taken out and the atria and right ventricle were removed. After refrigeration, the frozen heart was sliced into 5-6 sections, and the slices were incubated in 1% triphenyltetrazolium chloride (TTC). The slices were immersed in 10% formalin overnight. The infarcted myocardium was dissected from the IZS under the illumination of a dissecting microscope. IS, IZS and left ventricle were weighed. Heart...