title: Effects of water temperature on perchlorate toxicity to the thyroid and reproductive system of Oryzias latipes.
abstract: Water temperature is expected to increase in many parts of the world due to global climate change. The change in water temperature may affect ecosystems through alterations of the chemical properties or by affecting the susceptibility of organisms. Perchlorate can disrupt thyroid function of an organism by inhibiting iodide uptake. In the present study, the effect of water temperature on perchlorate toxicity was evaluated using Japanese medaka (Oryzias latipes). Pairs of adult medaka fish were exposed to a sublethal concentration of sodium perchlorate (100mg/L) and a control, at a 'low' (26°C), 'medium' (29°C) or 'high' water temperature (33°C) for seven days. The effects of the water temperature on reproduction, thyroid hormones and cortisol concentrations were determined. Transcription of several genes related to thyroid function and stress were also investigated. Significant down-regulation of thyroid hormone receptor alpha (THR-α) and beta (THR-β) transcripts and up-regulation of deiodinase 2 (DIO2) transcripts were observed in the fish exposed to perchlorate. Thyroxine (T4) concentrations were decreased, while triiodothyronine (T3) levels remained constant following exposure to perchlorate, and this effect became more pronounced under the high water temperature conditions (33°C). Up-regulation of the DIO2 gene may explain these observations. The total number of spawned eggs decreased slightly as the water temperature increased, and this reduction became significant when fish were exposed to perchlorate. Our observations indicate that exposure to perchlorate could affect thyroid function and overall reproductive fitness, and these effects could be aggravated under high water temperatures.
authors.affiliation: School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Sangwoo
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Occupational and Environmental Health, Yongin University, Yongin 449-714, Republic of Korea.
authors.forename: Kyunghee
authors.initials: K
authors.lastname: Ji
authors.affiliation: School of Public Health, Seoul National University, Seoul 151-742, Republic of Korea. Electronic address: kyungho@snu.ac.kr.
authors.forename: Kyungho
authors.initials: K
authors.lastname: Choi
mesh_terms: D000818:Animals; D015536:Down-Regulation; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D006358:Hot Temperature; D006854:Hydrocortisone / Q000097:blood; D009990:Oryzias; D010472:Perchlorates / Q000633:toxicity*; D011897:Random Allocation; D012098:Reproduction / Q000187:drug effects*; D017670:Sodium Compounds / Q000633:toxicity*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D015854:Up-Regulation; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D010472:Perchlorates; D017670:Sodium Compounds; D014874:Water Pollutants, Chemical; D014284:Triiodothyronine; C031068:sodium perchlorate; D000254:Sodium-Potassium-Exchanging ATPase; D013974:Thyroxine; D006854:Hydrocortisone
keywords: Climate change; Medaka; Stress biomarker; Thyroid; Thyroid hormone disruption