| Non-Human Toxicity Excerpts | /ENDOCRINE MODULATION/ Some phenols have been suspected to modulate the endocrine systems of wildlife and humans, but less is known about their interactions with different types of nuclear receptors. In this study, the ability of 2-tert-butylphenol, 2-isopropylphenol, 4-tert-octylphenol (4-t-OP), 2,4-dichlorophenol (2,4-DCP), 3,4-dichlorophenol (3,4-DCP), pentachlorophenol (PCP), bisphenols A (BPA), tetrabromobisphenol A (TBBPA), tetrachlorobisphenol A (TCBPA) and 4-phenylphenol to activate estrogen receptor (ER), androgen receptor (AR), progesterone receptor (PR) and estrogen-related receptor (ERR) were determined using a set of recombined yeast strains. It was found that 4-t-OP, 3,4-DCP, PCP, BPA, TBBPA, TCBPA and 4-phenylphenol were ERalpha agonists, while 4-t-OP, PCP and 4-phenylphenol showed ERalpha antagonistic activities. 2-tert-Butylphenol, 4-t-OP, 2-isopropylphenol, 2,4-DCP, 3,4-DCP, BPA, TCBPA and 4-phenylphenol were antagonists for AR, whereas none of the compounds studied were found to be an AR agonist. TCBPA, TBBPA and PCP were PR antagonists, and 2-tert-butylphenol, 3,4-DCP, 4-t-OP, 4-phenylphenol and 2-isopropylphenol were weak inhibitors on expression under control of the PR. None of the phenols were PR agonists. 2-tert-Butylphenol, 4-t-OP and PCP were ERRgamma inverse agonists, while 2,4-DCP, 3,4-DCP, PCP, BPA, TBBPA and TCBPA exhibited the ability to reverse the ERR inhibition induced by 4-hydroxytamoxifen. Based on the functional agonistic or antagonistic receptor-mediated effects, we further discussed the possible action mechanisms of these phenols as endocrine disrupting chemicals./ENDOCRINE MODULATION/ Previously, /the researchers/ transiently transfected Gal4-fused thyroid hormone receptor (TR) expressing vector and the Gal4 response reporter structure pUAS-tk-luc into HepG2 cell, developed a TR beta-1 mediated reporter gene assay to screen for compounds that acted on the TR signaling pathway. In this study, /the researchers/ improved the test efficiency by changing the transfected cell line into CV-1 cell. Triiodothyronine (T3) and thyroxine (T4) induced higher luciferase expression, with the median effective concentration (EC(50)) of 1.16 x 10(-8) and 1.36 x 10(-7)M, respectively. Bisphenol A (BPA) was selected as a positive antagonist, exhibiting weak anti-thyroid hormone activity with the median inhibitory concentration (IC(50)) of 1.64 x 10(-5)M. The assay showed acceptable repeatability to T3 with inter coefficient of variability (CV) of 27.5% and intra CV of 18.6%. Two flame retardants, tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA), were tested for their agonist and antagonist activities. As a result, /the researchers/ found that both of them possessed TR antagonist activity and neither of them showed agonist activity. These results suggested that TBBPA and TCBPA could act as TH antagonists. This assay provided a useful tool for the assessment of environmental chemicals as thyroid system disruptors./ENDOCRINE MODULATION/ The thyroid hormonal-disrupting activity of the flame retardants tetrabromobisphenol A and tetrachlorobisphenol A was examined and compared with that of bisphenol A, a typical estrogenic xenobiotic. Tetrabromobisphenol A and tetrachlorobisphenol A, halogenated derivatives of bisphenol A, markedly inhibited the binding of triiodothyronine (T(3)1 x 10(-10) M) to thyroid hormone receptor in the concentration range of 1 x 10(-6) to 1 x 10(-4) M, but bisphenol A did not. The thyroid hormonal activity of tetrabromobisphenol A and tetrachlorobisphenol A was also examined using rat pituitary cell line GH3 cells, which grow and release growth hormone (GH) depending on thyroid hormone. Tetrabromobisphenol A and tetrachlorobisphenol A enhanced the proliferation of GH3 cells and stimulated their production of GH in the concentration range of 1 x 10(-6) to 1 x 10(-4) M, while bisphenol A was inactive. Tetrabromobisphenol A, tetrachlorobisphenol A, and bisphenol A did not show antagonistic action, i.e., these compounds did not inhibit the hormonal activity of T(3) to induce growth and GH production of GH3 cells. Tetrabromobisphenol A and tetrachlorobisphenol A, as well as bisphenol A, enhanced the proliferation of MtT/E-2 cells, whose growth is estrogen-dependent. These results suggest that tetrabromobisphenol A and tetrachlorobisphenol A act as thyroid hormone agonists, as well as estrogens./ENDOCRINE MODULATION/ The endocrine-disrupting activities of bisphenol A (BPA) and 19 related compounds were comparatively examined by means of different in vitro and in vivo reporter assays. BPA and some related compounds exhibited estrogenic activity in human breast cancer cell line MCF-7, but there were remarkable differences in activity. Tetrachlorobisphenol A (TCBPA) showed the highest activity, followed by bisphenol B, BPA, and tetramethylbisphenol A (TMBPA)2,2-bis(4-hydroxyphenyl)-1-propanol, 1,1-bis(4-hydroxyphenyl)propionic acid and 2,2-diphenylpropane showed little or no activity. Anti-estrogenic activity against 17beta-estradiol was observed with TMBPA and tetrabromobisphenol A (TBBPA). TCBPA, TBBPA, and BPA gave positive responses in the in vivo uterotrophic assay using ovariectomized mice. In contrast, BPA and some related compounds showed significant inhibitory effects on the androgenic activity of 5alpha-dihydrotestosterone in mouse fibroblast cell line NIH3T3. TMBPA showed the highest antagonistic activity, followed by bisphenol AF, bisphenol AD, bisphenol B, and BPA. However, TBBPA, TCBPA, and 2,2-diphenylpropane were inactive. TBBPA, TCBPA, TMBPA, and 3,3'-dimethylbisphenol A exhibited significant thyroid hormonal activity towards rat pituitary cell line GH3, which releases growth hormone in a thyroid hormone-dependent manner. However, BPA and other derivatives did not show such activity. The results suggest that the 4-hydroxyl group of the A-phenyl ring and the B-phenyl ring of BPA derivatives are required for these hormonal activities, and substituents at the 3,5-positions of the phenyl rings and the bridging alkyl moiety markedly influence the activities.For more Non-Human Toxicity Excerpts (Complete) data for 2,2',6,6'-TETRACHLOROBISPHENOL A (10 total), please visit the HSDB record page. |
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