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Yu K, Li X, Qiu Y, Zeng X, Yu X, Wang W, Yi X, Huang L. Low-dose effects on thyroid disruption in zebrafish by long-term exposure to oxytetracycline. Aquat Toxicol 2020; 227:105608. [PMID: 32858424 DOI: 10.1016/j.aquatox.2020.105608] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 08/13/2020] [Accepted: 08/16/2020] [Indexed: 06/11/2023]
Abstract
As a feed additive in agriculture, the antibiotic oxytetracycline (OTC) has become widely distributed in the natural environment, leading to the exposure of many organisms to low doses of OTC. Although OTC is clinically contraindicated in children because of its multiple side effects, the effect of exposure to low doses of environmental OTC on children is unknown, particularly during development. In this study, we investigated the effects of OTC on the thyroid endocrine system in zebrafish, through determinations of the whole-body contents of triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) by enzyme-linked immunosorbent assay, and analysis of the mRNA expression of regulatory genes involved in the hypothalamus-pituitary-thyroid (HPT) axis using quantitative real-time polymerase chain reaction. Zebrafish embryos were exposed to OTC at environmentally relevant concentrations from 2 h to 120 days post-fertilisation. After exposure to OTC at 1,000 and 5,000 ng/L, T3 contents were significantly enhanced (37.8% and 45.1%, respectively) and TSH contents were reduced (16% and 16.3%, respectively) compared with those in the controls. The OTC-driven increase in the transcription of genes involved in thyroid synthesis (tpo and nis) may be responsible for the altered T3 levels. These data indicate that OTC may cause thyroid dysfunction and lead to reduced TSH secretion owing to enhanced negative feedback control of the HPT axis. Meanwhile, a decrease in body length, weight, and BMI and an increase in heart rate were observed with increasing OTC exposure. In conclusion, our results indicate that long-term exposure to low concentrations of OTC may alter the transcription of key genes involved in the HPT axis, as well as T3 and TSH contents, thereby disrupting the thyroid system and affecting the growth and development of zebrafish.
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Affiliation(s)
- Kan Yu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China; Department of Pediatrics, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China
| | - Xiaoyong Li
- Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China
| | - Yushu Qiu
- Department of Pediatrics, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China
| | - Xinxin Zeng
- Department of Pediatrics, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China
| | - Xiaogang Yu
- Municipal Key Lab of Environment and Children's Health, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China
| | - Weiye Wang
- Municipal Key Lab of Environment and Children's Health, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China.
| | - Xiaoping Yi
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.
| | - Lisu Huang
- Department of Pediatrics, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China.
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