Department of Integrative Biology, University of Guelph, Ontario, Canada.
Department of Integrative Biology, University of Guelph, Ontario, Canada.
Aquat Toxicol. 2020 Apr;221:105419. doi: 10.1016/j.aquatox.2020.105419. Epub 2020 Jan 20.
Petrogenic chemicals are common and widespread contaminants in the aquatic environment. In Canada, increased extraction of bitumen from the oil sands and transport of the major crude oil export product, diluted bitumen (dilbit), amplifies the risk of a spill and contamination of Canadian waterways. Fish exposed to sublethal concentrations of crude oil can experience a variety of adverse physiological effects including osmoregulatory dysfunction. As regulation of water and ion balance is crucial during the seawater transition of anadromous fish, the hypothesis that dilbit impairs seawater acclimation in Atlantic salmon smolts (a fish at risk of exposure in Canada) was tested. Smolts were exposed for 24 d to the water-soluble fraction of dilbit in freshwater, and then transferred directly to seawater or allowed a 1 wk depuration period in uncontaminated freshwater prior to seawater transfer. The seawater acclimation response was quantified at 1 and 7 d post-transfer using established hematological, tissue, and molecular endpoints including gill Na/K-ATPase gene expression (nka). All smolts, irrespective of dilbit exposure, increased serum Na concentrations and osmolality within 1 d of seawater transfer. The recovery of these parameters to freshwater values by 7 d post-transfer was likely driven by the increased expression and activity of Na/K-ATPase in the gill. Histopathological changes in the gill were not observed; however, CYP1A-like immunoreactivity was detected in the pillar cells of gill lamellae of fish exposed to 67.9 μg/L PAC. Concentration-specific changes in kidney expression of a transmembrane water channel, aquaporin 3, occurred during seawater acclimation, but were resolved with 1 wk of depuration and were not associated with histopathological changes. In conclusion, apart from a robust CYP response in the gill, dilbit exposure did not greatly impact common measures of seawater acclimation, suggesting that significant osmoregulatory dysfunction is unlikely to occur if Atlantic salmon smolts are exposed sub-chronically to dilbit.
石油成因化学物质是水生环境中常见且广泛存在的污染物。在加拿大，从油砂中提取更多的沥青以及运输主要的原油出口产品——稀释沥青（dilbit），增加了溢油和污染加拿大水道的风险。暴露于亚致死浓度原油的鱼类可能会经历各种不良生理效应，包括渗透调节功能障碍。由于在洄游鱼类向海水过渡期间，水和离子平衡的调节至关重要，因此测试了稀释沥青会损害大西洋鲑鱼苗（加拿大易受暴露影响的鱼类）的海水适应能力的假设。鱼苗在淡水中暴露于稀释沥青的水溶性部分 24 天，然后直接转移到海水中，或在无污染的淡水中进行 1 周的净化期，然后再转移到海水中。在转移后 1 天和 7 天，使用已建立的血液学、组织和分子终点（包括鳃 Na/K-ATP 酶基因表达（nka））量化了海水适应反应。所有鱼苗，无论是否暴露于稀释沥青，在转移到海水后 1 天内均增加了血清 Na 浓度和渗透压。在转移后 7 天内，这些参数恢复到淡水值可能是由于鳃中的 Na/K-ATP 酶表达和活性增加所致。在暴露于 67.9 μg/L PAC 的鱼类的鳃片柱细胞中检测到 CYP1A 样免疫反应，但未观察到鳃的组织病理学变化。在海水适应过程中，肾脏中一种跨膜水通道 aquaporin 3 的表达发生了浓度特异性变化，但在净化 1 周后得到解决，并且与组织病理学变化无关。总之，除了鳃中出现强烈的 CYP 反应外，稀释沥青暴露并未对海水适应的常见措施产生重大影响，这表明如果大西洋鲑鱼苗亚慢性暴露于稀释沥青，则不太可能发生显著的渗透调节功能障碍。
