Wang Zaosheng, Feng Chenglian, Ye Chun, Wang Youshao, Yan Changzhou, Li Rui, Yan Yijun, Chi Qiaoqiao
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Boulevard, Xiamen 361021, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Aquat Toxicol. 2016 Jul;176:10-23. doi: 10.1016/j.aquatox.2016.04.008. Epub 2016 Apr 14.
In this study, the effect of environmental metal exposure on the accumulation and subcellular distribution of metals in the digestive gland of clams with special emphasis on metallothioneins (MTs) was investigated. Specimens of indigenous Moerella iridescens were collected from different natural habitats in Maluan Bay (China), characterized by varying levels of metal contamination. The digestive glands were excised, homogenized and six subcellular fractions were separated by differential centrifugation procedures and analyzed for their Cu, Zn, Cd and Pb contents. MTs were quantified independently by spectrophotometric measurements of thiols. Site-specific differences were observed in total metal concentrations in the tissues, correlating well with variable environmental metal concentrations and reflecting the gradient trends in metal contamination. Concentrations of the non-essential Cd and Pb were more responsive to environmental exposure gradients than were tissue concentrations of the essential metals, Cu and Zn. Subcellular partitioning profiles for Cu, Zn and Cd were relatively similar, with the heat-stable protein (HSP) fraction as the dominant metal-binding compartment, whereas for Pb this fraction was much less important. The variations in proportions and concentrations of metals in this fraction along with the metal bioaccumulation gradients suggested that the induced MTs play an important role in metal homeostasis and detoxification for M. iridescens in the metal-contaminated bay. Nevertheless, progressive accumulation of non-essential metals (Cd, and especially Pb) resulting from "spillover" was observed in putative metal- sensitive (e.g., mitochondria and heat-denaturable protein (HDP)) or lysosome/microsome fractions, demonstrating that metal detoxification was incomplete and increased the toxicological risk to M. iridescens inhabiting the metal-impacted environments. Through multiple stepwise regression analysis, the induction of MTs was statistically correlated with the HSP concentrations of Cu, and to a lesser extent with Zn, and ultimately to the Cd concentrations, exhibiting significant dose-dependent relationships. Overall, these findings not only revealed the fates of accumulated metals, but scientifically favored an improved understanding of the detoxification at the subcellular level in response to metal accumulation, supporting the focus of metabolic availability assessment on the intracellular processes or events occurring within organisms.
在本研究中，调查了环境金属暴露对蛤消化腺中金属积累和亚细胞分布的影响，特别关注金属硫蛋白（MTs）。从中国马銮湾不同自然栖息地采集了本地的彩虹明樱蛤样本，这些栖息地具有不同程度的金属污染特征。切除消化腺，进行匀浆，通过差速离心程序分离出六个亚细胞组分，并分析其铜、锌、镉和铅含量。通过硫醇的分光光度测量独立定量MTs。在组织中的总金属浓度上观察到了特定地点的差异，这与可变的环境金属浓度密切相关，并反映了金属污染的梯度趋势。非必需金属镉和铅的浓度比必需金属铜和锌的组织浓度对环境暴露梯度更敏感。铜、锌和镉的亚细胞分配概况相对相似，热稳定蛋白（HSP）组分是主要的金属结合区室，而对于铅来说，该组分的重要性要小得多。该组分中金属比例和浓度的变化以及金属生物积累梯度表明，诱导产生的MTs在受金属污染海湾的彩虹明樱蛤的金属稳态和解毒中起重要作用。然而，在假定的金属敏感（如线粒体和热变性蛋白（HDP））或溶酶体/微粒体组分中观察到了由“溢出”导致的非必需金属（镉，尤其是铅）的逐渐积累，这表明金属解毒不完全，并增加了栖息在受金属影响环境中的彩虹明樱蛤的毒理学风险。通过多元逐步回归分析，MTs的诱导与铜的HSP浓度在统计学上相关，在较小程度上与锌相关，最终与镉浓度相关，呈现出显著的剂量依赖关系。总体而言，这些发现不仅揭示了积累金属的归宿，而且从科学上有助于更好地理解细胞水平上对金属积累的解毒作用，支持将代谢有效性评估重点放在生物体内发生的细胞内过程或事件上。
