Abstract 71: Soy Isoflavone Protects Myocardial Ischemia/reperfusion Injury Through Increasing Endothelial Nitric Oxide Synthase and Decreasing Oxidative Stress in Ovariectomized Rats

Rationale: There is a special role for estrogens in preventing and curing cardiovascular disease in women. Soy isoflavone (SI), a soy-derived phytoestrogen, is a group of biologically active plant substances with chemical structures which are similar to that of an endogenous estrogen-estradiol. Objective: We ought to elucidate possible mechanism of SI to improve myocardial ischemia/reperfusion (MI/R) injury in ovariectomized rats. Methods and Results: Female SD rats were underwent bilateral ovariectomy or sham ovariectomy. One week later, rats were randomly divided into several groups and began to feed soy-free chow: sham ovariectomy operation (control group), ovariectomy with MI/R or ovariectomy with sham MI/R. Other ovariectomy rats were given different doses of SI dissolved in 0.5% carboxymethycellulose (CMC-Na) by gavage. Additional ovariectomy rats were administrated with the same volume of CMC-Na by gavage or 50 μg/kg·d of 17β-estradiol (E 2 ) by subcutaneous injection. After four-week treatment, they were exposed to 30 minutes of left coronary artery occlusion followed by 6 or 24 hours of reperfusion. SI treatment decreased body weight, increased estradiol level and uterus weight. Isoflavone administration significantly reduced myocardial infarct size, improved left ventricle function and restored endothelium-dependent relaxation function of thoracic aortas after MI/R in ovariectomized rats. SI also decreased creatine kinase and malonaldehyde in plasma and attenuated oxidative stress in the myocardium. Meanwhile, SI increased phosphatidylinositol 3 kinase (PI3K) / Akt/ endothelial nitric oxide synthase (eNOS) signal pathway. Conclusion: Soy isoflavone protects myocardial ischemia/reperfusion injurys in ovariectomized rats through increasing PI3K/Akt/eNOS signal pathway and decreasing oxidative stress.