title: The progestin levonorgestrel affects sex differentiation in zebrafish at environmentally relevant concentrations.
abstract: Synthetic progestins have become widespread environmental contaminants and may cause adverse effects on fish. In the present study, we investigated the effects of levonorgestrel (LNG) on sex differentiation in zebrafish (Danio rerio). Embryos were exposed to LNG at environmentally relevant concentrations (0, 1, 10, 33, and 100ng/L) and allowed to develop until sexual maturity. Histological examination at 63 days post fertilization (dpf) caused complete sex reversal and 100% males were observed in the 10, 33 and 100ng/L treatments; gross morphological and histological examination of gonads at 142dpf further confirmed 100% males at these exposure concentrations. The results indicate androgenic activity of LNG, and masculinization during zebrafish gonadal differentiation. The mRNA expression levels of genes involved in fish sex differentiation and gonadal development were examined at 28 and 42dpf. Down-regulation of the mRNA expression of aromatase (e.g., cyp19a1a, cyp19a1b), the forkhead transcription factor gene L2 (foxl2) and the Fushi tarazu factor-1d (nr5a1b) were observed. In contrast, transcription of the doublesex and mab-3-related transcription factor 1 (dmrt1) gene was up-regulated. Androgen receptor (ar) mRNA expression was significantly down-regulated at 28 and 42dpf. Co-exposure to flutamide (an androgen antagonist) and LNG, led to a decrease in the sex inversion potency of LNG. Our study has demonstrated that environmentally relevant concentrations of LNG could alter sex differentiation and gonadal development in zebrafish. Our results also suggest a potentially high ecological risk of LNG to fish populations in LNG-contaminated aquatic environments.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Jianghuan
authors.initials: J
authors.lastname: Hua
authors.affiliation: Biology Institute of Shangdong Academy of Sciences, Jinan 250014, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Han
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
authors.forename: Yongyong
authors.initials: Y
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China. Electronic address: bszhou@ihb.ac.cn.
authors.forename: Bingsheng
authors.initials: B
authors.lastname: Zhou
mesh_terms: D000818:Animals; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D006066:Gonads / Q000187:drug effects; D016912:Levonorgestrel / Q000633:toxicity*; D008297:Male; D011944:Receptors, Androgen / Q000235:genetics; D012733:Sex Differentiation / Q000187:drug effects*; D014157:Transcription Factors / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish / Q000502:physiology*
chemical_list: D011944:Receptors, Androgen; D014157:Transcription Factors; D014874:Water Pollutants, Chemical; D016912:Levonorgestrel
keywords: Androgenic activity; Levonorgestrel; Progestin; Sex differentiation; Sex ratio; Zebrafish