Environment Canada, 105 McGill Street, Montréal, Quebec, Canada H2Y 2E7.
Comp Biochem Physiol B Biochem Mol Biol. 2012 Mar;161(3):261-7. doi: 10.1016/j.cbpb.2011.12.002. Epub 2011 Dec 10.
Microcystins (MC) are usually the predominant cyanotoxins associated with cyanobacterial blooms in natural surface waters. These toxins are well-known hepatotoxic agents that proceed by inhibiting protein phosphatase in aquatic biota; recent studies have also reported oxidative stress and disruption of ion regulation in aquatic organisms. In the present study, young trout (Oncorhynchus mykiss) were exposed to crude extracts of Microsystis aeruginosa for four days at 15 °C. The level of microcystins was calculated to confirm the presence of toxins in these crude extracts: 0, 0.75, 1.8 and 5 μg/L. Protein phosphatase measured in the liver increased by at least 3-fold and is significantly as a result of exposure to these sublethal concentrations of crude extract, his indicates an early defense response against protein phosphatase inhibition from cyanotoxins. This was corroborated by the decreased phosphate content in proteins found in the liver and brain. No increase in glutathione-S transferase (GST) activity was observed and lipid peroxidation was unaffected in both liver and brain tissue exposed to the cyanobacterial extracts. The data revealed that the proportion of the reduced (metal-binding) form of metallothionein (MT) decreased by two-fold relative to the control group (with a concomitant increase in the proportion of the oxidized form). The level of phosphate associated with MT increased by 1.5-fold at the highest concentration of crude extract. Acetylcholinesterase (AChE) activity in brain tissue was decreased after exposure to the highest concentration of crude extract, suggesting a slowdown in neural activity. However, no biotransformation processes or detoxification of GST was triggered. Our findings show early sign of biochemical effects of MC-LR in young trout.
微囊藻毒素（MC）通常是与天然地表水中蓝藻水华相关的主要藻毒素。这些毒素是众所周知的肝毒素，通过抑制水生生物中的蛋白磷酸酶起作用；最近的研究还报告了水生生物中的氧化应激和离子调节紊乱。在本研究中，将幼年虹鳟（Oncorhynchus mykiss）在 15°C 下暴露于铜绿微囊藻的粗提物中四天。计算微囊藻毒素的水平以确认这些粗提物中存在毒素：0、0.75、1.8 和 5μg/L。肝脏中测量的蛋白磷酸酶活性至少增加了 3 倍，并且由于暴露于这些亚致死浓度的粗提取物而显著增加，这表明了对来自藻毒素的蛋白磷酸酶抑制的早期防御反应。这与在肝脏和大脑中发现的蛋白质中的磷酸盐含量降低相吻合。在暴露于蓝藻提取物的肝脏和脑组织中未观察到谷胱甘肽-S-转移酶（GST）活性的增加，脂质过氧化也不受影响。数据显示，与对照组相比，金属结合型（金属结合）形式的金属硫蛋白（MT）的比例降低了两倍（同时氧化型比例增加）。与 MT 相关的磷酸盐水平在粗提取物的最高浓度下增加了 1.5 倍。暴露于粗提取物的最高浓度后，脑组织中的乙酰胆碱酯酶（AChE）活性降低，表明神经活动减慢。然而，没有触发 GST 的生物转化过程或解毒。我们的研究结果表明，MC-LR 在幼年虹鳟中表现出早期的生化效应。
