National Institute for Research in the Amazon, Department of Ecology, Laboratory of Ecophysiology and Molecular Evolution, Ave André Araújo 2936, 69083-000, Manaus, AM, Brazil.
Aquat Toxicol. 2010 Apr 15;97(2):134-41. doi: 10.1016/j.aquatox.2009.12.020. Epub 2010 Jan 4.
The main goal of this study was to investigate the toxicological effects of the chemical dispersant Corexit 9500, crude oil and the combination of the two components in the form of chemically dispersed crude oil (CO+DIS) on the ion regulation of the tropical fish tambaqui (Colossoma macropomum). Gill ion regulation was evaluated on the basis of unidirectional flux measurements (influx-J(in), efflux-J(out) and net flux-J(net)) of Na(+), Cl(-) and K(+). Plasma ion composition, haematocrit, haemoglobin and glucose concentrations in the blood of tambaqui were determined by classical methods. The exposure of fish to chemically dispersed crude oil promoted a significant increase in J(out) Na(+) across the gills, which, together with the inability of fish to stimulate Na(+) uptake to compensate for these losses resulted in significantly higher J(net) Na(+) outward, particularly within the first 3h of exposure. Increased outward J(net) Cl(-) was also seen in fish that were exposed to dispersed crude oil, whereas outward J(net) K(+) was only increased at crude oil dispersed in higher concentration of Corexit 9500. Plasma Na(+) and Cl(-) concentrations decreased between 6 and 12h of exposure, whereas Ca(2+) concentrations remained significantly lower than those of the control group over the entire experimental period. There were significant increases in plasma K(+) concentrations and in the haematocrit after 6 and 24h of exposure to dispersed crude oil, suggesting significant changes in the permeability of the erythrocytic membrane. Collectively, our results suggest that chemically dispersed crude oil promotes a more extensive impairment of gill ion regulation, in addition to changes in plasma ion levels and blood parameters, in tambaqui compared with exposure to Urucu crude oil or Corexit 9500 alone. Thus, in the event of an oil spill in Amazonian waters, the chemical dispersion of Urucu crude oil could represent a great risk to tambaqui, challenging their ability to maintain ionic and osmotic gradients in native ion-poor waters.
本研究的主要目的是研究化学分散剂 Corexit 9500、原油以及两者以化学分散原油（CO+DIS）形式组合对热带鱼巨臀脂鲤（Colossoma macropomum）离子调节的毒理学影响。通过单向通量测量（流入-J(in)、流出-J(out)和净通量-J(net)）评估了鳃的离子调节，测量了 Na(+)、Cl(-)和 K(+)。通过经典方法测定了巨臀脂鲤血液中的血浆离子组成、血细胞比容、血红蛋白和葡萄糖浓度。暴露于化学分散原油的鱼类鳃中 Na(+)的 J(out)显著增加，这与鱼类无法刺激 Na(+)摄取以补偿这些损失相结合，导致净 Na(+)外流显著增加，特别是在暴露的前 3 小时内。暴露于分散原油的鱼类中也观察到 Cl(-)的净 J(out)增加，而仅在 Corexit 9500 分散浓度较高的原油中才观察到 K(+)的净 J(out)增加。暴露 6 至 12 小时后，血浆 Na(+)和 Cl(-)浓度降低，而 Ca(2+)浓度在整个实验期间均显著低于对照组。暴露于分散原油 6 和 24 小时后，血浆 K(+)浓度和血细胞比容显著增加，表明红细胞膜通透性发生显著变化。总的来说，与单独暴露于 Urucu 原油或 Corexit 9500 相比，化学分散原油更广泛地损害了巨臀脂鲤的鳃离子调节，同时还改变了血浆离子水平和血液参数。因此，如果在亚马逊水域发生溢油事件，Urucu 原油的化学分散可能对巨臀脂鲤构成巨大风险，挑战它们在本地贫离子水中维持离子和渗透梯度的能力。
