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Developmental Exposure of Zebrafish (Danio rerio) to Tetrac, a T4 Analogue, Produces Persistent Maturational Effects
Citation:
Korest, D., S. Wesstrom, D. Hunter, AND S. Padilla. Developmental Exposure of Zebrafish (Danio rerio) to Tetrac, a T4 Analogue, Produces Persistent Maturational Effects. Carolinas SETAC, Charleston, South Carolina, May 17 - 19, 2017.
Impact/Purpose:
The thyroid axis plays a key role in embryonic development, but there is very little known about the longer term effects of early life thyroid perturbation. To assess later changes, zebrafish embryos/larvae were developmentally exposed to an analogue of the thyroid hormone, T4, early in development, and their growth and maturation tracked for the subsequent seven days.
Description:
The thyroid axis plays a key role in embryonic development. While the impact of thyroid hormone expression perturbation is documented in the early stages of zebrafish development, the effects on later developmental milestones are not well-delineated. To assess later changes, zebrafish embryos/larvae were developmentally exposed to an analogue of the thyroid hormone, T4, early in development, and their growth and maturation tracked for the subsequent seven days. Wild-type zebrafish embryos were treated with 3,3’,5,5’-tetraiodothyroacetic acid (Tetrac), at 0, 0.17, 1.7, 17.0 nM nominal concentration on 0 and 3 days post fertilization (dpf); at 5dpf larvae were moved out of the chemical solutions into vehicle only solution (depuration). Fry were removed (n=6/day) on days 10 through 13 for length measurement and visual (blinded) assessment of other developmental milestones (anterior swim bladder formation and separation, as well as caudal, dorsal, anal and pelvic fin development). At 13 dpf, fry treated with the 17 nM Tetrac were shorter than the other experimental groups (p < 0.012) and also failed to develop their anterior swim bladders (p <0.001). The anal and caudal ray fins developed normally in the 17 nM dose group relative to the control, but their dorsal and pelvic fins appeared to be more mature than controls at 13 dpf. In sum, concentrations of Tetrac that cause no lethality or malformations during the embryonic dosing period were capable of causing significant later effects, possibly by perturbing the developmental trajectory of the thyroid axis. This abstract may not necessarily reflect official Agency policy.