Ács A, Imre K, Kiss Gy, Csaba J, Győri J, Vehovszky Á, Farkas A
MTA ÖK Centre for Ecological Research, Balaton Limnological Institute, Tihany, 8237, Hungary.
Arch Environ Contam Toxicol. 2015 May;68(4):707-17. doi: 10.1007/s00244-015-0150-y. Epub 2015 Mar 24.
The multixenobiotic defense mechanism (MXR) in aquatic organisms was recognized as a first-line defense system, and its potential use as an early biomarker of exposure to environmental stress has raised attention in the last two decades. To evaluate the relevance of this biomarker in the freshwater mussel Dreissena polymorpha, we studied its responsiveness within laboratory exposures to contaminants sequestered in freshwater sediments affected by moderate anthropogenic impact. The effectiveness of this biomarker was assessed by comparing the MXR-transporter activities determined in bivalves first with toxicity scores recorded with the D. rerio embryo developmental assay. Both bioassays were applied in the sediment contact test format. As a second evaluation approach, MXR activities determined in exposed mussels were compared with sediment-contamination data integrated into toxic units on the basis of acute toxicity to Daphnia magna. In D. polymorpha subjected to acute exposure with moderately polluted sediments, we detected limited (22-33 %) but statistically significant induction of MXR activity. Mean MXR activities significantly correlated with TU values computed for test sediments. MXR activities in mussels showed strong positive correlation with the metal load of sediments and proved to be unrelated to the contamination with polycyclic aromatic compounds. MXR activity in laboratory-exposed mussels showed low variability within treatments and thus reliably reflected even low contaminant differences between the negative reference and moderately polluted harbor sediments. The strong correlation found in this study between the MXR-transporter activity in exposed mussels and environmentally realistic sediment contamination underscores the fairly good sensitivity of this biomarker in laboratory testing conditions to signal the bioavailability of sediment bound contaminants, and it may also anticipate even the incidence of toxicity to biota.
水生生物中的多异生物质防御机制（MXR）被认为是一种一线防御系统，在过去二十年中，其作为环境应激暴露早期生物标志物的潜在用途引起了关注。为了评估这种生物标志物在淡水贻贝多形饰贝中的相关性，我们研究了其在实验室暴露于受中度人为影响的淡水沉积物中所含污染物时的反应性。通过将双壳类动物中测定的MXR转运蛋白活性首先与斑马鱼胚胎发育试验记录的毒性评分进行比较，评估了这种生物标志物的有效性。两种生物测定均采用沉积物接触试验形式。作为第二种评估方法，将暴露贻贝中测定的MXR活性与基于大型溞急性毒性整合到毒性单位中的沉积物污染数据进行比较。在多形饰贝急性暴露于中度污染沉积物的情况下，我们检测到MXR活性有有限的（22%-33%）但具有统计学意义的诱导。平均MXR活性与测试沉积物计算的毒性单位值显著相关。贻贝中的MXR活性与沉积物的金属负荷呈强正相关，并且证明与多环芳烃污染无关。实验室暴露贻贝中的MXR活性在处理组内显示出低变异性，因此即使阴性对照和中度污染港口沉积物之间的污染物差异很小也能可靠地反映出来。本研究中暴露贻贝的MXR转运蛋白活性与环境实际沉积物污染之间的强相关性强调了这种生物标志物在实验室测试条件下对沉积物结合污染物生物可利用性信号的相当好的敏感性，并且它甚至可能预测对生物群的毒性发生率。
