Osman A M, Rotteveel S, den Besten P J, van Noort P C M
Institute for Inland Water Management and Waste Water Treatment, PO Box 17, 8200 AA Lelystad, The Netherlands.
J Appl Toxicol. 2004 Mar-Apr;24(2):135-41. doi: 10.1002/jat.963.
The principal aim of this study was to assess whether the two quinones, menadione (2-methyl-1,4-naphthoquinone) and lawsone (2-hydroxy-1,4-naphthoquinone), elicit differential toxicity in mussels as has been reported for higher organisms. Therefore, the effects of short-term (48 h) and long-term (20 days) exposure of the two quinones at concentrations of 0.56 and 1 mg l(-1) to zebra mussels, Dreissena polymorpha, under laboratory conditions were studied. After the short-term exposure, the specific activities of the two-electron quinone oxidoreductase (DT-diaphorase) and the one-electron catalysing quinone reductases NADPH-cytochrome c reductase and NADH-cytochrome c reductase were determined in the gills and the rest of the soft tissues (soft mussel tissues minus the gills) of both treated and control mussels. At the higher concentrations of menadione and lawsone used, a significant reduction of the activity of NADPH-cytochrome c reductase in the gills and in the rest of the soft mussel tissues (by 33-34% and 31-43%, respectively) was observed. The activities of DT-diaphorase and NADH-cytochrome c reductase were not significantly affected. Interestingly, DT-diaphorase was observed in the gills, an organ requiring protection against antioxidants. Furthermore, a single-cell electrophoretic assay (comet assay) performed with gill cells to assess DNA damage by the quinones did not show any significant difference between the treated and the control organisms. This indicates that the formation of reactive species by the quinone metabolism in vivo in the mussels was possibly suppressed through the concerted action of DT-diaphorase and antioxidant enzymes. The results of in vitro experiments with gill extracts confirmed the protective role of DT-diaphorase. The rate of the two-electron quinone reduction was found to be five times that of the one-electron quinone reduction. The results of the long-term exposure unambiguously demonstrated that in mussels menadione, unlike in higher organisms, is more toxic than lawsone. The lack of detectability of xanthine oxidase in the mussel tissues could explain the comparatively lower toxicity of lawsone in the invertebtrate, lending support to a previous suggestion that xanthine oxidase might be responsible for the mechanism of toxicity of lawsone in higher organisms in vivo.
本研究的主要目的是评估两种醌类物质，即甲萘醌（2-甲基-1,4-萘醌）和紫铆因（2-羟基-1,4-萘醌），是否如针对高等生物所报道的那样，在贻贝中引发不同的毒性。因此，研究了在实验室条件下，将这两种醌类物质以0.56和1 mg l(-1)的浓度对斑马贻贝（Dreissena polymorpha）进行短期（48小时）和长期（20天）暴露的影响。短期暴露后，测定了处理组和对照组贻贝鳃以及其余软组织（贻贝软组织减去鳃）中双电子醌氧化还原酶（DT-黄递酶）以及单电子催化醌还原酶NADPH-细胞色素c还原酶和NADH-细胞色素c还原酶的比活性。在所使用的较高浓度的甲萘醌和紫铆因条件下，观察到鳃和其余贻贝软组织中NADPH-细胞色素c还原酶的活性显著降低（分别降低33 - 34%和31 - 43%）。DT-黄递酶和NADH-细胞色素c还原酶的活性未受到显著影响。有趣的是，在鳃中观察到了DT-黄递酶，鳃是一个需要抗氧化剂保护的器官。此外，用鳃细胞进行单细胞电泳分析（彗星试验）以评估醌类物质对DNA的损伤，结果显示处理组和对照组生物之间没有任何显著差异。这表明贻贝体内醌类物质代谢产生的活性物质的形成可能通过DT-黄递酶和抗氧化酶的协同作用受到了抑制。鳃提取物的体外实验结果证实了DT-黄递酶的保护作用。发现双电子醌还原速率是单电子醌还原速率的五倍。长期暴露的结果明确表明，在贻贝中，与高等生物不同，甲萘醌比紫铆因毒性更大。贻贝组织中未检测到黄嘌呤氧化酶，这可以解释紫铆因在无脊椎动物中相对较低的毒性，这支持了之前的一种观点，即黄嘌呤氧化酶可能是紫铆因在高等生物体内毒性机制的原因。
