Nagel S C, vom Saal F S, Thayer K A, Dhar M G, Boechler M, Welshons W V
Division of Biological Sciences, University of Missouri-Columbia 65211, USA.
Environ Health Perspect. 1997 Jan;105(1):70-6. doi: 10.1289/ehp.9710570.
We have developed a relative binding affinity-serum modified access (RBA-SMA) assay to determine the effect of serum on the access of xenoestrogens to estrogen receptors within intact cultured MCF-7 human breast cancer cells. We used this assay to predict low dose activity of two xenoestrogens in mice. In serum-free medium, bisphenol A, a component of polycarbonates and of resins used to line metal food cans, showed a lower relative binding affinity (RBA; 0.006%) than octylphenol (0.072%) and nonylphenol (0.026%), which are used as surfactants in many commercial products (all RBAs are relative to estradiol, which is equal to 100%). In 100% serum from adult men, bisphenol A showed a higher RBA (0.01%) than in serum-free medium and thus enhanced access to estrogen receptors relative to estradiol. In contrast, octylphenol showed a 22-fold decrease in RBA (0.0029%) and nonylphenol showed a 5-fold decrease in RBA (0.0039%) when measured in adult serum. This indicates that, relative to estradiol, serum had less of an inhibitory effect on the cell uptake and binding in MCF-7 cells of bisphenol A, while serum had a greater inhibitory effect on octylphenol and nonylphenol relative to estradiol. Extrapolation of these relative activities in adult serum predicted that the estrogenic bioactivity of bisphenol A would be over 500-fold greater than that of octylphenol in fetal mouse serum. Bisphenol A and octylphenol were fed to pregnant mice at 2 and 20 micrograms/kg/day. Exposure of male mouse fetuses to either dose of bisphenol A, but to neither dose of octylphenol, significantly increased their adult prostate weight relative to control males, which is consistent with the higher predicted bioactivity of bisphenol A than octylphenol in the RBA-SMA assay. In addition, our findings show for the first time that fetal exposure to environmentally relevant parts-per-billion (ppb) doses of bisphenol A, in the range currently being consumed by people, can alter the adult reproductive system in mice.
我们开发了一种相对结合亲和力-血清修饰通路（RBA-SMA）测定法，以确定血清对完整培养的MCF-7人乳腺癌细胞中异源雌激素与雌激素受体结合的影响。我们使用该测定法预测了两种异源雌激素在小鼠体内的低剂量活性。在无血清培养基中，双酚A（聚碳酸酯和用于金属食品罐内衬的树脂的一种成分）的相对结合亲和力（RBA；0.006%）低于辛基酚（0.072%）和壬基酚（0.026%），后两者在许多商业产品中用作表面活性剂（所有RBA均相对于雌二醇，雌二醇等于100%）。在成年男性的100%血清中，双酚A的RBA（0.01%）高于无血清培养基中的RBA，因此相对于雌二醇，其与雌激素受体的结合能力增强。相比之下，在成年血清中测量时，辛基酚的RBA下降了22倍（0.0029%），壬基酚的RBA下降了5倍（0.0039%）。这表明，相对于雌二醇，血清对双酚A在MCF-7细胞中的细胞摄取和结合的抑制作用较小，而血清对辛基酚和壬基酚相对于雌二醇的抑制作用较大。根据成年血清中的这些相对活性推断，在胎鼠血清中，双酚A的雌激素生物活性比辛基酚高500倍以上。将双酚A和辛基酚以2和20微克/千克/天的剂量喂给怀孕小鼠。雄性胎鼠暴露于任何一个剂量的双酚A，但未暴露于任何一个剂量的辛基酚时，相对于对照雄性，其成年前列腺重量显著增加，这与RBA-SMA测定法中双酚A比辛基酚具有更高的预测生物活性一致。此外，我们的研究结果首次表明，胎儿暴露于目前人们正在摄入的十亿分之几（ppb）剂量的环境相关双酚A，可改变小鼠的成年生殖系统。
