2019: Fluoride and thyroid function in Zebrafish

All adverse health effects of fluoride are related to thyroid hormone metabolism.
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2019: Fluoride and thyroid function in Zebrafish

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Guo Wenjing, Wang T, Xue W, et al. - "Interference effects of fluoride on thyroid endocrine function in Zebrafish" Acta Scientiae Circumstantiae 39(4):1340-1347 (2019)
https://www.actasc.cn/hjkxxb/ch/reader/ ... 001&flag=1
https://global.cnki.net/kcms/detail/det ... X201904037
(Note time and dose-dependent bi-phasic effects)

Abstract:In order to investigate the interference effects of fluoride on thyroid endocrine function in female zebrafish, healthy female zebrafish were exposed to different concentrations of fluoride(0, 20, 40, 80 mg·L-1) for 45 and 90 days to measure the growth and development index, the thyroid microstructure by histological method, the levels of T3 and T4 in plasma by enzyme-linked immunosorbent assay(ELISA), and the expressions of endocrine-related mRNA in hypothalamus-pituitary-thyroid(HPT) axis by Quantitative Real-time PCR. The results showed that the growth and development index had a decreasing trend in fluoride-exposed groups with the increase of exposure concentration and time compared with the control group(p<0.05). The lesion degree of thyroid tissue was aggravated with the increase of exposure dose and time. The levels of T3 and T4 had an increasing trend after exposure for 45 days, while the T4 level had a decreasing trend and was significantly reduced in 80 mg·L-1 fluoride group after exposure for 90 days (p<0.05). After exposure for 45 days, all detected mRNA levels were significantly decreased in 40 mg·L-1 fluoride group except crh mRNA(p<0.05), while the mRNA levels were remarkably reduced in 80 mg·L-1 fluoride group except mRNA of tg, nis, ttr(p<0.05). After exposure for 90 days, the expressions of tg, dio1, dio2 mRNA were obviously elevated in 40 and 80 mg·L-1 fluoride groups(p<0.05), while the ugt1ab mRNA levels were significantly decreased in 80 mg·L-1 fluoride group(p<0.05). These results demonstrated that fluoride could disturb the thyroid endocrine function of female zebrafish by affecting the tissue structure of thyroid, the hormone levels, and the mRNA expressions in HPT axis, which inhibited the growth and development. All above provides the theoretical data for the ecotoxic effects and risk assessment of fluoride in aquatic environment.
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