Wade Michael G, Lee Alice, McMahon Avril, Cooke Gerard, Curran Ivan
Environmental & Occupational Toxicology Division, Healthy Environments & Consumer Safety Branch, Room 315, Environmental Health Centre, PL 0803D, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0L2.
Food Chem Toxicol. 2003 Nov;41(11):1517-25. doi: 10.1016/s0278-6915(03)00168-6.
Current in vivo methods to identify and assess reproductive hazards of endocrine disrupting substances are often confounded by the presence of isoflavones (genistein, diadzein, glycitein), strongly hormonally-active substances, in the diet of laboratory rodents. However, studies that have attempted to study the influence of dietary isoflavone on qualitative and quantitative uterotrophic responses have been limited by the few doses of isoflavone tested, stress to the animals due to changing of the diet immediately prior to testing and/or comparing effects of diets of very different composition. The current study examined the effects of isoflavone on uterotrophic response by using immature female rats reared from conception on diets varying only in the amount of isoflavone concentrate (Novasoy) added to a virtually isoflavone-free soya-based diet. The effects of these diets, and a soya-free semipurified diet (AIN 93G) on uterotrophic responses to treatment with a strong (Ethinyl Estradiol, EE) or a weak (bisphenol A, BPA) estrogenic substance were examined. The pups were treated with subcutaneous injections of either EE (1 microg/kg/day), BPA (600 mg/kg/day) or corn oil (vehicle) control for 3 days starting at weaning on post natal day (PND) 21. On the morning of PND 24 pups were sacrificed and uterus weight, epithelium labeling index (Bromo deoxyuridine incorporation), uterine epithelium thickness, and peroxidase activity were determined. Diet did not influence unstimulated uterine weight, epithelial height or peroxidase activity except at the highest isoflavone diet where animals had significantly increases in all three endpoints. Uterine weight, epithelial thickness and peroxidase were all significantly increased by EE or BPA treatment. There was no evidence of diet-induced potentiation or inhibition of the stimulatory actions of either EE or BPA on either uterine weight or epithelial thickness while EE-induced increase in uterine peroxidase activity was increased synergistically by the highest dose of isoflavone. A similar response to the latter effect was seen in BPA treated animals although this response was not significantly different from that of BPA treated rats fed the isoflavone-free soy diet. The rate of endometrial epithelium labeling with BrdU was not altered by any treatment. These results indicate that dietary isoflavone content can directly influence uterine weight and other estrogen-dependent endpoints demonstrating the potential of these to reduce the active range of the uterotrophic assay. However, there is no indication that isoflavones impair or potentiate the stimulatory action of either strong (EE) or weaker (BPA) estrogen agonists on uterine weight or epithelial morphology although the data do suggest the potential for synergy between high isoflavone content and estrogen agonist in inducing uterine peroxidase.
目前用于识别和评估内分泌干扰物质生殖危害的体内方法,常因实验室啮齿动物饮食中存在异黄酮(染料木黄酮、黄豆苷元、黄豆黄素)这种具有强烈激素活性的物质而受到干扰。然而,试图研究膳食异黄酮对子宫营养定性和定量反应影响的研究,受到所测试异黄酮剂量少、测试前因饮食改变对动物造成的应激以及/或者比较成分差异极大的饮食效果等因素的限制。本研究通过使用从受孕开始饲养的未成熟雌性大鼠,来检测异黄酮对子宫营养反应的影响,这些大鼠食用的是仅在基于大豆的几乎不含异黄酮的饮食中添加不同量异黄酮浓缩物(Novasoy)的日粮。研究了这些日粮以及一种不含大豆的半纯化日粮(AIN 93G)对用强效(乙炔雌二醇,EE)或弱效(双酚A,BPA)雌激素物质处理后的子宫营养反应的影响。幼崽在出生后第21天(PND)断奶时开始,皮下注射EE(1微克/千克/天)、BPA(600毫克/千克/天)或玉米油(赋形剂)对照,持续3天。在PND 24的早晨处死幼崽,测定子宫重量、上皮标记指数(溴脱氧尿苷掺入)、子宫上皮厚度和过氧化物酶活性。日粮对未受刺激的子宫重量、上皮高度或过氧化物酶活性没有影响,除非在异黄酮含量最高的日粮组,该组动物这三个指标均显著增加。EE或BPA处理均显著增加了子宫重量、上皮厚度和过氧化物酶活性。没有证据表明日粮会诱导增强或抑制EE或BPA对子宫重量或上皮厚度的刺激作用,而EE诱导的子宫过氧化物酶活性增加在异黄酮最高剂量时呈协同增加。在BPA处理的动物中也观察到了对后一种效应的类似反应,尽管这种反应与喂食不含异黄酮大豆日粮的BPA处理大鼠的反应没有显著差异。用BrdU标记子宫内膜上皮的速率不受任何处理的影响。这些结果表明,膳食异黄酮含量可直接影响子宫重量和其他雌激素依赖性指标,表明其有可能缩小子宫营养测定的活性范围。然而,没有迹象表明异黄酮会损害或增强强效(EE)或弱效(BPA)雌激素激动剂对子宫重量或上皮形态的刺激作用,尽管数据确实表明高异黄酮含量与雌激素激动剂在诱导子宫过氧化物酶方面存在协同作用的可能性。