以生物配體模式為基礎探討不同化學組成水域中銅對吳郭魚之生物可獲取率、次細胞分布及成長毒性

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Title:	以生物配體模式為基礎探討不同化學組成水域中銅對吳郭魚之生物可獲取率、次細胞分布及成長毒性
Authors:	蔡正偉(Tsai, Jeng-Wei);吳淑美
Contributors:	生命科學院生態暨演化生物學研究所
Date:	2012-07-31
Issue Date:	2012-06-15 16:57:03 (UTC+8)
Abstract:	進行水生生物的重金屬慢性暴露風險預測通常十分困難，主因為金屬之慢性毒不僅由化學物質在標的器官的累積量決定，水體中的陽離子會對金屬離子的生物可獲取率產生極大競爭效應以及生物在長期暴露過程的適應機制與對累積金屬的代謝能力亦佔有極重要決定因素。本三年期研究計畫將提出一以生物配體模式(biotic ligand model, BLM)為基礎的研究架構，探討影響銅在莫三比克種吳郭魚(Oreochromis mossambicus)的生物可獲取率(bioavailability)、次細胞層次分布 (subcellular partition)、及毒性作用模態(mode of action)等機制，以提升對不同水化學組成條件養殖區中之銅暴露風險預測能力。第一年，我們將開發慢性毒 BLM，我們也將量化主要器官在不同水化學組成條件下，對於銅的吸收以及排除速率常數，以了解水中陽離子以及溶解性有機物對銅的生物bioavailability 以及生物動力學(biokinetic)程序的影響。第二年，我們將利用BLM 以及損害評估模式(damage assessment model, DAM)對生物有效性以及毒性作用機制的理論為基礎，建構出一個可預測不同水化學組成、不同銅濃度條件的生物累積模式(water chemistry-based bioaccumulation model, WCBM)；同時，為解釋在慢性暴露條件下吳郭魚對銅的調控與適應策略，我們將進行一系列次細胞層次分布的實驗，並依據結果建構出一個次細胞分配模型(subcellular partition model, SPM)，來描述及預測在不同曝露條件下，銅在主要器官的有效活性濃度。第三年，我們將結合在第二年時完成的WCBM 以及SPM 以整合出一個全面性風險評估架構，並提出一個可預測吳郭魚各生命階段之成長毒性模式；我們將進行長期野外暴露實驗，以所獲得的水化學及生態毒理資料作為此一風險評估架構的驗證依據；最後我們將對野外實際的養殖池或生態系進行暴露風險預測，並提出水質管理標準以提供養殖風險管理或生態復育參考。 Long-term metal exposure risk assessment for aquatic organism is a challenge because the chronic toxicity of chemical is not only determined by the amount of accumulated chemical but also affected by the bioavailability, ability of biological regulation or detoxification of biota. The objective of this 3-year study proposal is to develop a mechanistic-based study framework to explicitly incorporate the factors controlling the bioavailability, subcellular regulation/distribution, and mode of action (MOA) to enhance predictive ability of chronic copper (Cu) toxicity to protect the health of site-specific farmed tilapia Oreochromis mossambicus. In the 1st year of the study, we will develop a chronic Cu biotic ligand model (BLM) for tilapia. The biokinetic parameters (uptake rate and depuration rate constants) of selected target organs in different exposure conditions will be measured. In the 2nd year, BLM and damage assessment model (DAM) will be mechanistically combined to develop a water chemistry-based bioaccumulation model (WCBM) for elucidating the site-specific temporal changes of Cu bioavailability To reveal how the tilapia regulating and acclimating to the chemical stress during chronic exposures, a series of subcelluar partition bioassays and a subcellular partion model (SPM) will be developed to quantitatively depict the time course of active Cu dose in the target organ. In the 3rd year of this proposal, we are going to develop a comprehensive biologically-based framework (including the knowledge of bioavailability, biokinetics, MOA, and biodynamics of copper toxicity) for assessing the chronic copper exposure risk by linking the WCBM and SPM that have been developed in the second year. We will identify the MOA of copper to tilapia in different life stages (embryos, larvae, juveniles and adults) and life-stage growth toxicity models will then be developed. We will conduct in-situ field experiments to validate the proposed modeling framework. Finally, the life-span copper exposure risk in real aquacultural fish farms or field aquatic ecosystems will be assessed and the criterion for aquacultral management or ecological conservation will be suggested.
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