Canada's oil sands industry continues to expand and the volume of diluted bitumen (dilbit) transported across North America is increasing, adding to spill risk and environmental contamination. Dilbit exposure is known to cause adverse effects in fish, but linking molecular and cellular changes with ecologically-relevant individual performance metrics is needed to better understand the potential consequences of a dilbit spill into the aquatic environment. Therefore, this study examined the effects of dilbit exposure on subcellular responses in cardiac and skeletal muscle in relation to swimming performance in a migratory fish species at risk of exposure, Atlantic salmon. Smolts were exposed subchronically to environmentally relevant concentrations of the water-soluble fraction of dilbit (WSFd) for 24 d, and then a subset of exposed fish underwent a depuration period of 7 or 14 d, for a total of 3 experimental time points. At each time point, repeat swimming performance was assessed using sequential critical swimming speed tests (Ucrit) separated by a 24 h rest period, and then several tissues were collected to determine biotransformation enzyme activation, energetic responses, and gene expression changes. Ucrit was unaffected in fish exposed to 67.9 μg/L total initial polycyclic aromatic compounds (PAC), but fish showed a decreased reliance on lipid metabolism for adenosine triphosphate (ATP) in the heart that was maintained through 7 d depuration. In contrast, Ucrit increased in fish exposed to 9.65 μg/L PAC, corresponding to an increased reliance on anaerobic metabolic pathways in cardiac and red skeletal muscle, with partial recovery after 7 d depuration. As expected, at both concentrations WSFd hepatic cyp 1A-mediated biotransformation reactions increased, as measured by EROD activity, which remained elevated for 7 d but not after 14 d depuration. Transcript abundance of cyp1a was also increased in muscle tissue and recovered by 14 d depuration. The expression of other stress-related genes increased in white muscle of dilbit-exposed fish, but were largely unchanged in cardiac and red muscle. The transcriptional profile of cardiac tissue was compared to that of sockeye salmon similarly exposed to WSFd in a previous experiment, and is provided in supplemental text. Combined, these results demonstrate that dilbit exposure alters gene expression and enzyme activities related to xenobiotic exposure, cellular stress, and muscle energetics in juvenile Atlantic salmon without impairing swimming performance, and that most of these changes are recoverable within 14 d depuration.

中文翻译：

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稀释沥青暴露对大西洋鲑鱼熏鲑的影响：与游泳表现有关的分子和代谢反应。

加拿大的油砂行业不断发展，稀释后的沥青（假人）在北美的运输量正在增加，这增加了泄漏风险和环境污染。众所周知，假阳具接触会对鱼类造成不利影响，但是需要将分子和细胞的变化与与生态相关的个体性能指标联系起来，以更好地了解假阳具泄漏到水生环境中的潜在后果。因此，本研究研究了在有暴露风险的迁徙鱼类大西洋鲑鱼中，与人接触游泳后，与之相比，假阳具暴露对心脏和骨骼肌亚细胞反应的影响。软体动物亚慢性暴露于与环境有关的浓度的Dilbit水溶性部分（WSFd）中24 d，然后对一部分裸露的鱼进行7或14 d的净化期，总共3个实验时间点。在每个时间点，使用相隔24小时的休息时间的连续临界游泳速度测试（Ucrit）评估重复游泳的表现，然后收集几个组织以确定生物转化酶的激活，能量反应和基因表达的变化。暴露于总初始多环芳族化合物（PAC）为67.9μg/ L的鱼中，乌里克特不受影响，但鱼的心脏对三磷酸腺苷（ATP）的脂类代谢依赖性降低了，并通过净化7 d得以维持。相比之下，暴露于9.65μg/ L PAC的鱼中的黑素含量增加，这对应于对心肌和红色骨骼肌厌氧代谢途径的依赖增加，净化7天后部分恢复。如预期的那样，在两种浓度下，通过EROD活性测定，WSFd肝cyp 1A介导的生物转化反应均增加，在净化7天后仍保持升高，但在净化14天后仍未升高。cyp1a的转录本丰度也在肌肉组织中增加，并在14 d净化后恢复。其他与应激有关的基因的表达在暴露于迪尔比特鱼的白肌肉中增加，但在心肌和红肌肉中基本没有变化。在先前的实验中，将心脏组织的转录特征与同样暴露于WSFd的红鲑鱼的转录特征进行了比较，并在补充文本中提供。综合起来，这些结果表明，dilbit暴露会改变与异源生物暴露，细胞应激，