Ramamoorthy K, Vyhlidal C, Wang F, Chen I, Safe S, McDonnell D P, Leonard L S, Gaido K W
Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, USA.
Toxicol Appl Pharmacol. 1997 Nov;147(1):93-100. doi: 10.1006/taap.1997.8281.
The estrogenic activity of 2',4',6'-trichloro-4-biphenylol (HO-PCB3), 2',3',4',5'-tetrachloro-4-biphenylol (HO-PCB4), and an equimolar mixture of both compounds (HO-PCB3/HO-PCB4) was investigated in the 21-day-old B6C3F1 mouse uterus, MCF-7 and MDA-MB-231 human breast cancer cells, HepG2 cells, and in a yeast-based reporter gene assay. Treatment of the animals with 17beta-estradiol (E2) (0.02 microg/kg/day x3) resulted in increased uterine wet weight, peroxidase activity and progesterone receptor binding. Treatment with 18, 73, 183 or 366 micromol/kg (x3) doses of HO-PCB3, HO-PCB4, or HO-PCB3/HO-PCB4 (equimolar) caused a dose-dependent increase in estrogenic activity; a maximal-induced response was not observed at any dose and the activity of the mixture was additive. Binding of E2, HO-PCB3, HO-PCB4, and HO-PCB3/HO-PCB4 to the mouse uterine estrogen receptor (ER) was determined in a competitive binding assay using [3H]E2 as the radioligand. The IC50 values were 1.1 x 10(-8), 3.4 x 10(-6), 9.9 x 10(-7), and 4.25 x 10(-6) m, respectively. HO-PCB3 and HO-PCB4 maximally induced MCF-7 cell proliferation, rat creatine kinase, and human complement C3 (C3-LUC) reporter gene activity at concentrations of 10(-5) to 10(-6) m, and these compounds were 10(3) to 10(4) less potent than E2. The HO-PCB3/HO-PCB4 mixture was active at the high concentration (10(-5) m) and was additive for these responses. HO-PCB3 and HO-PCB4 also exhibited estrogenic activity in human HepG2 cells cotransfected with C3-LUC and an ER expression plasmid, and the estrogenic activity of the HO-PCB mixture was additive. Similar results were obtained in yeast transformed with the human ER and a double estrogen responsive element upstream of the beta-gal reporter gene. The effects of variable ER expression on the potential synergistic interactions of HO-PCB3/HO-PCB4 were investigated in HepG2 cells cotransfected with C3-LUC (405 ng/well) and variable amounts of ER expression plasmid (270, 27, 2.7, or 0.27 ng/well). The results show that as ER levels decreased, the magnitude of the induction response by E2, HO-PCB3, HO-PCB4, and HO-PCB3/HO-PCB4 also decreased. However, the activities of the HO-PCB mixture were additive at high and low levels of ER. Similar results were obtained in MDA-MB-231 cells cotransfected with C3-LUC and variable amounts of ER expression plasmid. The results of this study demonstrate that for several estrogen-responsive assays in the mouse uterus; MCF-7, HepG2, and MDA-MBA-231 human cancer cells; and a yeast based-reporter gene assay, both HO-PCB3 and HO-PCB4 exhibited estrogenic activity. The estrogenic activity of an equimolar mixture of these compounds was additive at high and low levels of ER expression.
在21日龄的B6C3F1小鼠子宫、MCF-7和MDA-MB-231人乳腺癌细胞、HepG2细胞以及基于酵母的报告基因分析中，研究了2',4',6'-三氯-4-联苯酚（HO-PCB3）、2',3',4',5'-四氯-4-联苯酚（HO-PCB4）以及这两种化合物的等摩尔混合物（HO-PCB3/HO-PCB4）的雌激素活性。用17β-雌二醇（E2）（0.02μg/kg/天×3）处理动物，导致子宫湿重、过氧化物酶活性和孕酮受体结合增加。用18、73、183或366μmol/kg（×3）剂量的HO-PCB3、HO-PCB4或HO-PCB3/HO-PCB4（等摩尔）处理，引起雌激素活性呈剂量依赖性增加；在任何剂量下均未观察到最大诱导反应，且混合物的活性是相加的。在以[3H]E2作为放射性配体的竞争性结合分析中，测定了E2、HO-PCB3、HO-PCB4和HO-PCB3/HO-PCB4与小鼠子宫雌激素受体（ER）的结合。IC50值分别为1.1×10^(-8)、3.4×10^(-6)、9.9×10^(-7)和4.25×10^(-6)m。HO-PCB3和HO-PCB4在浓度为10^(-5)至10^(-6)m时最大程度地诱导MCF-7细胞增殖、大鼠肌酸激酶和人补体C3（C3-LUC）报告基因活性，并且这些化合物的效力比E2低10^3至10^4倍。HO-PCB3/HO-PCB4混合物在高浓度（10^(-5)m）时具有活性，并且对于这些反应是相加的。HO-PCB3和HO-PCB4在用C3-LUC和ER表达质粒共转染的人HepG2细胞中也表现出雌激素活性，并且HO-PCB混合物的雌激素活性是相加的。在用人类ER和β-半乳糖苷酶报告基因上游的双雌激素反应元件转化的酵母中获得了类似结果。在用C3-LUC（405 ng/孔）和不同量的ER表达质粒（270、27、2.7或0.27 ng/孔）共转染的HepG2细胞中，研究了可变ER表达对HO-PCB3/HO-PCB4潜在协同相互作用的影响。结果表明，随着ER水平降低，E2、HO-PCB3、HO-PCB4和HO-PCB3/HO-PCB4的诱导反应幅度也降低。然而，HO-PCB混合物的活性在高和低ER水平时都是相加的。在用C3-LUC和不同量的ER表达质粒共转染的MDA-MB-231细胞中获得了类似结果。本研究结果表明，对于小鼠子宫、MCF-7、HepG2和MDA-MBA-231人癌细胞中的几种雌激素反应性分析以及基于酵母的报告基因分析，HO-PCB3和HO-PCB4均表现出雌激素活性。这些化合物的等摩尔混合物的雌激素活性在高和低ER表达水平时是相加的。
