腹泻性贝类毒素暴露途径及在贝类中代谢过程研究

Diarrhetic shellfish toxins (DSTs) easily accumulate in filter-feeding invertebrates via the food chain, and consumption of DSTs-contaminated seafood will lead to severe and occasionally fatal. The exposure routes and metabolic process are decisive factors that influence levels of DSTs in shellfish samples. Previous studies have indicated that the peak value of DSTs in shellfish sometimes does not coincide with the corresponding abundance of toxic algae in the seawaters, suggesting that the exposure routes of DSTs by shellfish are not only derived from toxic algal cells but also from other pathways (such as dissolved DSTs in the seawater and suspended solids and sediment adsorbed with DSTs). However, there are no studies on the exposure routes of DSTs by shellfish. Commonly occurring DSTs are lipophilic and can be classified as free and combined forms. Previous studies often ignore the combined DSTs and it could not accurately reflect the metabolic processes of DSTs in shellfish. In summary, the present study proposed that there may exist variety of exposure pathways of DSTs by shellfish, combined with laboratory simulating exposure experiments of shellfish, using the analytical method of liquid chromatography-mass spectrometry, according to the law of by mass conservation law to explore the process of accumulation, transformation and discharge of DSTs in different species of shellfish, combining the biodynamic model to perfect metabolic model of DSTs in shellfish. This project can help provide the basic information and theoretical basis for illustrating the characteristics of DSTs contaminated by shellfish, and complete the dynamic process of metabolism of DSTs in shellfish, and preventing the poisoning of marine products.

腹泻性贝类毒素（diarrhetic shellfish toxins, DSTs）可经食物链而蓄积于海洋贝类，进而危及消费者安全。暴露途径和代谢过程是决定贝毒素含量的关键因素。贝中DSTs含量峰值有时与水体中对应有毒藻细胞丰度并不吻合，推测其不仅来源于有毒藻细胞，也可能来源于其他途径（如溶解态DSTs或固体悬浮物和沉积物吸附的DSTs）。但目前尚未有关于DSTs暴露途径研究。DSTs有自由态和结合态之分，以往研究常忽视结合态DSTs，不能准确反映DSTs在贝内代谢过程。综上所述，本研究首次提出贝类可能存在多种暴露DSTs途径，结合室内模拟贝类染毒实验，运用液-质联用分析方法，通过质量守恒定律来探讨各形态DSTs在不同贝类中累积、转化和排出过程，结合生物动力学模型完善其在贝中代谢模型。本项目对阐明贝类染毒特征，完善DSTs在贝内代谢动态过程，防范水产品中毒事件，能够提供基础资料和理论依据。

腹泻性贝类毒素（Diarrhetic Shellfish Toxins, DSTs）是近海海洋环境中极具广泛分布性和危害性的一类藻毒素，贝类等生物是DSTs传播的重要生物媒介。阐明DSTs在代表性贝类体内中的代谢过程可为海洋环境监测、水产品中毒事件防范等提供基础资料和理论依据。通过开展本项目，发现包括腹泻性贝类毒素的脂溶性藻毒素成分广泛分布于海洋环境中，包括贝类、浮游植物、海水、悬浮物和沉积物等介质中，这说明藻毒素在海洋环境中是广泛存在的，这也揭示出贝类等生物沾染藻毒素的途径是多样化的。室内通过培养产毒藻种利玛原甲藻（Prorocentrum lima）获取腹泻性贝类毒素成分（大田软海绵酸OA和鳍藻毒素DTX1），构建溶解态藻毒素暴露体系，实验室模拟进一步证实翡翠贻贝（Perna viridis）和菲律宾蛤仔（Ruditapes philippinarum）等代表性的经济型贝类可快速累积水体中溶解态的腹泻性贝类毒素成分，且自由态和结合态毒素成分是DSTs在贝类组织中两种主要的存在形式，自由态的OA和DTX1能够与贝类组织中脂肪酸形成酰化产物，主要形式为R-C7-O-acyl，结合态毒素经酶解作用可又转化成自由态形式，这说明自由态和结合态的腹泻性贝类毒素在藻-贝间存在着酰化为主导的转化过程，且不同贝类中腹泻性贝类毒素的形态转化和代谢过程存在一定的相似性。本研究同时表明贝类可快速累积水体中溶解态的DSTs，这表明贝类等生物不仅能够通过滤食产毒藻细胞获取藻毒素，还能通过其他可能的途径获取藻毒素，该研究结果扩展了藻毒素在海洋环境中的行为研究。