銀鱗鯧(Monodactylus argenteus)屬於海洋廣鹽性硬骨魚類，在台灣是一種常見的觀賞魚類。亞硝酸鹽為水生環境中的潛在問題。現今普遍採集約式養殖法，這些方法將會造成累積亞硝酸鹽而導致毒性的風險。當銀鱗鯧面臨急毒性濃度的亞硝酸時，所誘發的分子生理反應機制之探討仍相當缺乏。本篇研究將銀鱗鯧稚魚暴露於濃度為0, 25, 50, 75, 100 and 150 mg/L NO2−N之亞硝酸鹽中進行96小時亞硝酸鹽急毒性試驗，確認半致死濃度(96 h - LC50)為54.5 (42.5-67.9) mg/L NO2−N。本篇研究再進一步利用銀鱗鯧來探討暴露在亞致死亞硝酸鹽濃度2 mM海水為期七日期間，其生長、離子調控、形質層次及分子層次等生理反應。實驗結果顯示，暴露在亞硝酸鹽濃度2 mM銀鱗鯧的肝指數有下降的趨勢而其血漿葡萄糖、血漿氯離子濃度及血漿滲透壓皆有上升的趨勢。暴露在亞硝酸鹽濃度2 mM其鰓上Na⁺-K⁺-ATPase的表現量明顯高於控制組(P < 0.05 )。在鰓、肝上的熱休克蛋白70 (Heat shock protein 70; HSP70)及熱休克蛋白90 (Heat shock protein 90; HSP90)的結果顯示，暴露在亞硝酸鹽濃度2 mM其表現量顯著上升(P < 0.05 )。銀鱗鯧在鰓、肝上的泛素蛋白(Ubiquitin-conjugated proteins)在亞硝酸曝露下並無顯著變化。根據本研究的結果發現，當銀鱗鯧暴露在亞致死的亞硝酸鹽濃度時，藉由活化Na⁺-K⁺-ATPase反應和蛋白質恆定機轉以調整其離子調節反應及蛋白質的穩定來對抗亞硝酸鹽逆境的刺激。綜合以上結果，本研究闡明亞致死濃度的亞硝酸逆境，對魚類多方面的生理影響，希望本研究的結果能提供相關的研究資料用於評估亞硝酸鹽對廣鹽性硬骨魚類之影響。

Silver moony (Monodactylus argenteus) is a common aquarium ornamental species in Taiwan. Due to study on nitrite toxicity in silver moony is lack, an acute toxicity test was carried out by exposing the juvenile fish to 0, 25, 50, 75, 100 and 150 mg/L NO2−N for 96 h. The determined median lethal concentration (96 h - LC50) was 54.5 (42.5-67.9) mg/L NO2−N. The impacts of sublethal nitrite exposure were further investigated. After exposure to 28 mg/L (2 mM) NO2−N for 7 days, decrease of hepasomatic index and increase in plasma glucose levels, osmolality and chloride concentration were observed. Gill Na+/K+-ATPase (NKA) response elevated in silver moony when exposed to sublethal nitrite. In protein quality control (PQC) mechanism, expression of branchial and hepatic heat shock protein (HSP) 90 and 70 up-regulated in response to sublethal nitrite exposure while the levels of ubiquitin-conjugated proteins were constant. The present study showed that sublethal nitrite exposure might be a stressor to affect ionic balance and homeostasis of cellular proteins, and then activation of NKA responses and PQC mechanism was essential for ionoregulatory adjustment and protein stability. This study provided the information to clarify the potential treats of sublethal nitrite toxicity to multi-physiological regulation of seawater teleosts.

論文審定書 i
誌謝 ii
摘要 iii
ABSTRACT iv
List of Figures viii
List of Table ix
1. Introduction 1
2. Materials and methods 4
2.1. Experimental animals and environments 4
2.2. Acute toxicity of nitrite 4
2.3. Sublethal nitrite exposure 6
2.4. Calculation of condition factor (CF) and hepatosomatic index (HSI) 6
2.5. Analysis of plasma glucose, osmolality, chloride concentration and muscle water content (MWC) 7
2.6. Antibodies 7
2.7. Preparation of gill and liver homogenates 8
2.8. Immunoblotting 9
2.9. Specific activity of NKA 10
2.10. Statistical analyses 12
3. Results 12
3.1. 96 h median lethal concentration (96 h - LC50) of nitrite 12
3.2. Ionoregulatory responses to sublethal nitrite exposure 12
3.3. Stress responses to sublethal nitrite exposure 13
3.4. Impacts of sublethal nitrite exposure on morphometric indices 14
4. Discussion 15
References 20
Figures 27
Table 37

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