金雀异黄酮通过减少卵巢切除大鼠心肌小凹蛋白-1的表达而增加一氧化氮的生成

观察金雀异黄酮(genistein)替代治疗对卵巢切除大鼠心肌中一氧化氮(nitric oxide,NO)和内皮型一氧化氮合酶(endothelial nitric oxide synthase,eNOS)的影响.成年雌性Sprague-Dawley大鼠经双侧卵巢切除术,假手术组作为对照,术后三周将行卵巢切除术的大鼠随机分为低剂量genistein(0.5 mg/kg·d1)、高剂量genistein(5.0 mg/kg·d-1)、17-β雌二醇(0.1 mg/kg·d-1)和模型组(100μl/d芝麻油),各组均皮下注射给药并给予不含大豆的饲料喂养6周,测定大鼠尾动脉血压、心率,麻醉后放血处死大鼠称量子宫重量;放免法检测血浆中总雌二醇,亚硝酸还原酶法检测心肌匀浆中NO,Western blot检测心肌中eNOS的表达以及eNOS的调节蛋白小凹蛋白-1(caveolin-1)和钙调素(calmodulin)的表达情况.结果显示各组间大鼠血压无显著性差异,同17-β雌二醇一样,genistein能呈剂量依赖性地增加心肌组织中eNOS表达量和NO生成,同时genistein能明显降低内源性eNOS活性抑制物caveolin-1的表达,而不影响eNOS活性正性调节蛋白钙调素的表达.与溶媒对照组比较,0.5 mg/kg·d-1的genistein不增加子宫重量,5.0 mg/kg·d-1的genistein增加子宫重量3倍,但较17-β雌二醇(增加6倍)的作用小(P＜0.01).上述结果提示,植物雌激素genistein剂量依赖性地上调心肌组织eNOS的活性并增加NO的生成,减少抑制eNOS活性的小凹蛋白-1表达.

Phytoestrogen genistein supplementation increases eNOS and decreases caveolin-1 expression in ovariectomized rat hearts

This study examined whether genistein influences the production of nitric oxide (NO) and expression of endothelial nitric oxide synthase (eNOS) and the modulators of eNOS activity in ovariectomized (OVX) rat hearts. Female mature Sprague-Dawley rats were subjected to bilateral ovariectomy, OVX rats were randomly divided into four groups: 17beta-estradiol (0.1 mg/kg, s.c. daily) was used as the positive control; low dose of genistein (0.5 mg/kg, s.c. daily); high dose of genistein (5.0 mg/kg, s.c. daily) and model. Sham operations as controls, the treatment lasted 6 weeks. Blood pressure, heart rate, plasma estradiol, heart and uterine weights were measured. Nitrite production in the myocardium was determined by nitrate reductase method. Protein level of eNOS, caveolin-1 and calmodulin was determined by Western blot. The results showed that nitrite production and eNOS protein in homogenized ventricular tissue was attenuated by approximately 53% and 67% in OVX rats compared with those in sham rats, respectively. Genistein increased nitrite production in rat heart in a dose-dependent manner, genistein at the dose of 5 mg/kg.d(-1) resumed nitrite production to a level similar to that in sham operated rats. Administration of genistein also increased eNOS protein expression in OVX rats myocardium with a concomitant decrease in the expression of caveolin-1, an endogenous eNOS inhibitory protein. Another eNOS stimulatory protein, calmodulin, was unchanged in these treatments. These effects were also observed in rats treated with 17beta-estradiol. Genistein at the dose of 5.0 mg/kg.d(-1) augmented uterine weight but this side effect in reproductive system was less than that of 17beta-estradiol. These results suggest that genistein supplementation and estrogen replacement therapy directly increase eNOS functional activity and NO production in the hearts of the OVX rats, but genistein has less side effects on the reproductive system than 17beta-estradiol.