碩士 / 國立臺灣大學 / 農業化學研究所 / 102 / Phthalates are synthetic plasticizers commonly used in industry to enhance the flexibility and softness of plastic products. Among these phthalates, di(2-ethylhexyl)phthalate (DEHP) is the most common plasticizer in the world. It is easily leached into the environment and ubiquitously detected in surface water in many countries including Taiwan. Recent studies have indicated that DEHP is an endocrine disrupting chemical (EDC) in experimental animals. It is considered that DEHP exposure will retard development of reproductive organs and impair physiological function. However, studies directly linking to environmental relevant concentrations are still limited. The impact and associated toxic mechanism of DEHP on environmental aquatic life is unclear at present. The objective of the study is to investigate the toxic effect of DEHP on fish reproduction using medaka (Orzyias latipes) fish as the model organism. We have treated pairs of sexually matured adults of female leucophore free II (FLFII) medaka with DEHP at environmentally relevant concentrations 20, 100 and 200 μg/L for a 21-day aqueous exposure and assess their reproduction performance. Fish were used for analyses of plasma concentrations of sex hormone at the end of exposure, activities of antioxidant enzymes and gene expression in different organs. Our results show that DEHP at 20-200 μg/L decreased fecundity, and also inhibited the expression of phase I enzymes (cyp1a and cyp3a40) in liver. In gill, antioxidant enzymes such as catalase (CAT) and glutathione S-transferase (GST), the phase II enzyme, activities were decreased with 100-200 μg/L DEHP. DEHP may interfere xenobiotics metabolism of medaka through inhibiting expression of both phase I and phase II enzymes. Furthermore, gene expression of sod, cat and gpx were interfered in liver and gonads with DEHP treatments (20-200 μg/L). In female liver, cat was induced, but gpx was inhibited. On the other hand, both sod and gpx were inhibited in male liver, suggesting the defense against oxidative stress was altered. In addition, sod induction and cat and gpx inhibition were observed in ovaries. The DEHP-induced oxidative stress in ovaries may obstruct female reproductive function, and then decrease fecundity. In conclusion, environmentally relevant concentrations of DEHP caused reproductive toxicity in medaka. The activities and gene expression of antioxidant enzymes were altered by DEHP exposure in liver, gill and gonad, indicating oxidative stress and interference of xenobiotics metabolism. DEHP is an ubiquitous environment contaminant of emerging concern, so it is important to evaluate the risk to ecosystem.
| Identifer | oai:union.ndltd.org:TW/102NTU05406001 |
| Date | January 2014 |
| Creators | Ming-Huei Lin, 林明慧 |
| Contributors | Pei-Jen Chen, 陳佩貞 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 100 |
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