Smital Tvrtko, Sauerborn Roberta, Hackenberger Branimir K
Department for Marine and Environmental Research, Laboratory for Molecular Ecotoxicology, Rudjer Boskovic Institute, PO Box 180, Bijenicka 54, 10 000 Zagreb, Croatia.
Aquat Toxicol. 2003 Dec 10;65(4):443-65. doi: 10.1016/s0166-445x(03)00175-9.
Previous investigations directed to the determination of the P-glycoprotein (Pgp) expression in aquatic organisms have indicated the possibility of the multixenobiotic resistance mechanism (MXR) induction as a response to organic pollution. However, in numerous cases no significant and/or no clear relationship between Pgp contents and pollution level was detected. Concerning these discrepancies the results of an extensive, 3-year study of the Pgp mediated MXR induction in the selected freshwater (Dreissena polymorpha) and marine (Mytilus galloprovincialis) bivalves are presented here. The main goals of the study were to ascertain the rate-dynamic, level, as well as the possible usability of MXR in environmental biomonitoring. Since the primary result of MXR induction should be the decreased intracellular accumulation of xenobiotics, the determination of MXR induction was performed using the measurement of Pgp transport activity. We measured the accumulation or the efflux rate of the model Pgp substrate rhodamine B (RB) in gills of the mussels previously exposed to pollution. The study was performed in several steps: from the exposure experiments in laboratory, using model inducers rhodamine 123 (R123) and water extract of Diesel-2 oil (D2), to the final in situ testing in real environmental conditions. Our results confirmed that Pgp activity is induced/induces according to the level of pollution, and that 4-days period was already long enough for the significant induction and deinduction of MXR activity. However, the inducibility of Pgp transport activity was significantly limited--the maximal level of induction obtained in this study resulted in 50-60% lower RB accumulation in the gills of induced specimens (laboratory or in situ exposed to pollution), when compared to control, non-induced animals. The obtained level of Pgp related MXR induction, resulting in halfway lesser accumulation of a model pollutant (RB), extrapolated to the similar scenario with toxic xenobiotics may have significant environmental relevance. However, our results also suggest that for the use of the MXR as a relevant biomarker the Pgp transport activity should be measured along with the determination of DNA, mRNA or/and protein expression. Based on the data from this study several factors that may have had critical influence on the effectiveness and the level of MXR induction are additionally discussed.
此前针对水生生物中P-糖蛋白（Pgp）表达的测定研究表明，多异种生物抗性机制（MXR）有可能作为对有机污染的一种反应而被诱导。然而，在许多情况下，并未检测到Pgp含量与污染水平之间存在显著和/或明确的关系。针对这些差异，本文介绍了一项为期3年的广泛研究结果，该研究针对选定的淡水双壳贝类（多形饰贝）和海洋双壳贝类（地中海贻贝）中Pgp介导的MXR诱导情况展开。该研究的主要目标是确定MXR的速率动态、水平以及其在环境生物监测中的可能适用性。由于MXR诱导的主要结果应该是异生物质在细胞内的积累减少，因此通过测量Pgp转运活性来进行MXR诱导的测定。我们测量了预先暴露于污染环境的贻贝鳃中模型Pgp底物罗丹明B（RB）的积累或流出速率。该研究分几个步骤进行：从实验室的暴露实验开始，使用模型诱导剂罗丹明123（R123）和柴油-2油（D2）的水提取物，到最终在实际环境条件下进行原位测试。我们的结果证实，Pgp活性根据污染水平被诱导，并且4天的时间对于MXR活性的显著诱导和去诱导已经足够长。然而，Pgp转运活性的诱导能力受到显著限制——与未诱导的对照动物相比，本研究中获得的最大诱导水平导致诱导标本（在实验室或原位暴露于污染环境）鳃中RB的积累降低了50 - 60%。所获得的与Pgp相关的MXR诱导水平，导致模型污染物（RB）的积累减少一半，外推到有毒异生物质的类似情况可能具有重要的环境意义。然而，我们的结果还表明，为了将MXR用作相关生物标志物，应在测定DNA、mRNA或/和蛋白质表达的同时测量Pgp转运活性。基于本研究的数据，还额外讨论了可能对MXR诱导的有效性和水平产生关键影响的几个因素。
