T-screen and yeast assay for the detection of the thyroid-disrupting activities of cadmium, mercury, and zinc
2016
Li, Jian | Liu, Yun | Kong, Dongdong | Ren, Shujuan | Li, Na
In the present study, a two-hybrid yeast bioassay and a T-screen were used to screen for the thyroid receptor (TR)-disrupting activity of select metallic compounds (CdCl₂, ZnCl₂, HgCl₂, CuSO₄, MnSO₄, and MgSO₄). The results reveal that none of the tested metallic compounds showed TR-agonistic activity, whereas ZnCl₂, HgCl₂, and CdCl₂ demonstrated TR antagonism. For the yeast assay, the dose–response relationship of these metallic compounds was established, and the concentrations producing 20 % of the maximum effect of ZnCl₂, HgCl₂, and CdCl₂ were 9.1 × 10⁻⁵, 3.2 × 10⁻⁶, and 1.2 × 10⁻⁶ mol/L, respectively. The T-screen also supported the finding that ZnCl₂, HgCl₂, and CdCl₂ decreased the cell proliferation at concentrations ranging from 10⁻⁶ to 10⁻⁴ mol/L. Furthermore, the thyroid-disrupting activity of metallic compounds in environmental water samples collected from the Guanting Reservoir, Beijing, China was evaluated. Solid-phase extraction was used to separate the organic extracts, and a modified two-hybrid yeast bioassay revealed that the metallic compounds in the water samples could affect thyroid hormone-induced signaling by decreasing the binding of the thyroid hormone. The addition of ethylenediaminetetraacetic acid (30 mg/L) could eliminate the effects. Thus, the cause(s) of the thyroid toxicity in the water samples appeared to be partly related to the metallic compounds.
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