Pain Sandrine, Parant Marc
Université Paul Verlaine Metz, Laboratoire Ecotoxicité et Santé Environnementale, CNRS UMR 7146, Rue du Général Delestraint, 57 070 Metz, France.
Chemosphere. 2007 Apr;67(6):1258-63. doi: 10.1016/j.chemosphere.2006.11.017. Epub 2007 Jan 10.
The biological defence mechanism called MXR or MXD for multixenobiotic resistance or defence protects cells against the entry and the accumulation of xenobiotics. As the defence is modulated by man made chemicals, MXR is used as a biomarker of organisms' exposure to environmental contamination. However, to reliably assess and evidence MXR induction, the use of a reference level is required. In this context, we focused on MXR background level in a freshwater bivalve, the zebra mussel Dreissena polymorpha, in order to propose its use as a reference during MXR evaluation. We monitored the MXR transport activity in mussels collected either in a natural population or in a caged population and then transplanted to clean water in the laboratory. The results showed that MXR activity was decreased to its baseline level after an eight to nine day depuration period (13.1+/-3.1; 7+/-2.6; 13.7+/-3.9 pmol RB min(-1)org(-1) after three experiments of laboratory depurations). Moreover, significant MXR induction was measured in depurated zebra mussels exposed to contaminated sites (39.6+/-3.7; 59.2+/-20.3 pmol RB min(-1)org(-1) after two experiments of field exposure), showing that the laboratory depuration did not affect the induction potential. The MXR responses (decrease as well as increase) occurred in few days and were highly significant, highlighting its reactivity in zebra mussels. Finally, this paper confirms the usefulness of MXR as a tool in biomonitoring studies and provides a protocol for field experiments that enables to establish and use the background level of MXR activity as a reference.
被称为多异生物质抗性（MXR）或多异生物质防御（MXD）的生物防御机制可保护细胞免受异生物质的侵入和积累。由于这种防御机制受人造化学物质的调节，MXR被用作生物体接触环境污染的生物标志物。然而，为了可靠地评估和证明MXR的诱导作用，需要使用一个参考水平。在此背景下，我们重点研究了淡水双壳贝类斑马贻贝（Dreissena polymorpha）的MXR背景水平，以便在MXR评估过程中提出将其用作参考。我们监测了从自然种群或笼养种群中采集，然后移植到实验室清洁水中的贻贝的MXR转运活性。结果表明，经过八到九天的净化期后，MXR活性降至基线水平（经过三次实验室净化实验后，分别为13.1±3.1；7±2.6；13.7±3.9 pmol RB min⁻¹ org⁻¹）。此外，在暴露于污染场地的净化后的斑马贻贝中检测到显著的MXR诱导（经过两次野外暴露实验后，分别为39.6±3.7；59.2±20.3 pmol RB min⁻¹ org⁻¹），表明实验室净化并未影响诱导潜力。MXR反应（降低以及升高）在几天内就发生了，且非常显著，突出了其在斑马贻贝中的反应性。最后，本文证实了MXR作为生物监测研究工具的有用性，并提供了一个野外实验方案，该方案能够建立并使用MXR活性的背景水平作为参考。
