Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Institution of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, 510301, China.
Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Institution of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, 510301, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Aquat Toxicol. 2019 Jul;212:110-119. doi: 10.1016/j.aquatox.2019.05.001. Epub 2019 May 7.
Arsenic (As) is a highly toxic metalloid to aquatic organisms, but the effects of low-dose chronic inorganic As exposure on marine fish are still unclear. A 28-day study was conducted on chronic exposure of 100 μg/L inorganic As [As(III) and As(V)] in the marine medaka Oryzias melastigma to quantify the effects of chronic inorganic As exposure on its bioaccumulation, biotransformation, oxidative stress, and antioxidant enzymes response. During the exposure period, chronic inorganic As exposure had no significant effect on the total As bioaccumulation except at 7 d for As(V) treatment. Based on the toxicokinetic data, the low As bioaccumulation was caused by low dissolved uptake (k), internal transfer (k, k) and high efflux (k). The organic As were the predominated species (77 - 80%) and remained constant, while the inorganic As increased 35% (from 0.26 μg/g to 0.35 μg/g) during the initial 4-d exposure and then recovered. The increased inorganic As could be covered by the high contribution of organic As especially arsenobetaine (AsB) to the total As accumulation. Coincidently, the malondialdehyde (MDA) levels followed similar trends as the inorganic As concentrations, indicating that inorganic As bioaccumulation induced oxidative stress at the initial stage. Both the contents of the nonenzymatic antioxidant (glutathione, GSH) and the activities of the enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-S-transferase (GST)) increased initially and then decreased as the inorganic As concentrations, thus lowering the hydrogen peroxide (HO) levels and displaying a typical antioxidant defense mechanism. In summary, this study elucidated that although the marine medaka had a limited ability to accumulate waterborne As, the increase in the inorganic As at the early stage of exposure still caused toxic effects, which could be ignored by constant total As concentrations. Therefore, the toxicity of As could be underestimated if only the total As instead of the inorganic As is monitored in marine fish.
砷（As）是一种对水生生物具有高度毒性的类金属，但低剂量慢性无机砷暴露对海洋鱼类的影响仍不清楚。本研究进行了为期 28 天的慢性暴露实验，即在海洋青鳉（Oryzias melastigma）中暴露于 100μg/L 的无机砷[As（III）和 As（V）]，以量化慢性无机砷暴露对其生物积累、生物转化、氧化应激和抗氧化酶反应的影响。在暴露期间，慢性无机砷暴露除了在 As（V）处理的第 7 天外，对总砷生物积累没有显著影响。基于毒代动力学数据，低砷生物积累是由低溶解摄取（k）、内部转移（k，k）和高外排（k）引起的。有机砷是主要的砷形态（77-80%）且保持不变，而在最初的 4 天暴露期间，无机砷增加了 35%（从 0.26μg/g 增加到 0.35μg/g），然后恢复。增加的无机砷可以被有机砷，特别是砷甜菜碱（AsB）对总砷积累的高贡献所掩盖。巧合的是，丙二醛（MDA）水平与无机砷浓度呈相似趋势，表明在初始阶段，无机砷生物积累诱导了氧化应激。非酶抗氧化剂（谷胱甘肽，GSH）的含量和酶抗氧化剂（超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）和谷胱甘肽-S-转移酶（GST））的活性最初增加，然后随着无机砷浓度的降低而降低，从而降低了过氧化氢（HO）水平，并表现出典型的抗氧化防御机制。总之，本研究表明，尽管海洋青鳉对水中砷的积累能力有限，但在暴露初期无机砷的增加仍会产生毒性作用，而总砷浓度可能会忽略这一点。因此，如果仅监测海洋鱼类的总砷而不是无机砷，可能会低估砷的毒性。
