Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Aquat Toxicol. 2011 May;103(1-2):85-91. doi: 10.1016/j.aquatox.2011.02.013. Epub 2011 Feb 18.
The objective of the study was to examine the impact of municipal wastewater effluents on the functioning of the cortisol stress axis in rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were caged upstream (reference) and downstream (100% and 10% effluent) of a tertiary-treated municipal wastewater treatment plant outfall and sampled at 14d later (0 time samples). A second set of fish were then subjected to a 5 min handling disturbance and sampled at 1 and 24h post-stressor exposure. Plasma cortisol, glucose and lactate concentrations, liver and brain glucocorticoid receptor (GR) protein levels, head kidney mRNA abundances of corticosteroidogenesis genes, including steroidogenic acute regulatory protein (StAR), cytochrome P450 side chain cleavage (P450scc), 11β-hydroxylase and melanocortin 2 receptor (MC2R), and key liver metabolic enzyme activities, were measured. Exposure to effluent for 14d significantly elevated plasma cortisol and lactate levels in 100% effluent group compared to the reference and 10% effluent sites. There was a significantly higher StAR mRNA abundance in the effluent groups compared to the upstream control. GR protein levels in the liver, but not the brain, were significantly higher in the 100% effluent group compared to the upstream control group. Chronic exposure to 100% effluent for 14d significantly lowered liver hexokinase and glucokinase activities, but did not affect glycogen content or the activities of phosphoenolpyruvate carboxykinase, pyruvate kinase, lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase compared to the other two groups. Subjecting these fish to a secondary acute stressor elicited a physiological stress response, including significant transient elevation in plasma cortisol, glucose and lactate levels at 1h which dropped to pre-stress levels at 24h after stressor exposure, in the control and 10% effluent groups, but this conserved stress response was impaired in the 100% effluent group. The 100% effluent group fish also had significantly higher StAR and P450scc mRNA abundances at 1h post-stress, while transcript abundances of all the major corticosteroidogenesis genes were suppressed at 24h post-stressor compared to the control and 10% effluent groups. Considered together, exposure to full-strength MWWE for 14d elicits a chronic stress response in rainbow trout, and perturbs the conserved adaptive response to an acute stressor. Our results reveal that the impact of tertiary-treated MWWE on stress performance in rainbow trout is abolished by 90% effluent dilution.
本研究旨在探究城市污水对虹鳟（Oncorhynchus mykiss）皮质醇应激轴功能的影响。将幼龄虹鳟分别置于经三级处理的城市污水处理厂出水口的上游（对照）和下游（100%和 10%污水）的网箱中，14 天后（0 时间样本）采样。然后，第二组鱼受到 5 分钟的处理干扰，并在应激暴露后 1 和 24 小时采样。测量了血浆皮质醇、葡萄糖和乳酸浓度、肝脏和大脑糖皮质激素受体（GR）蛋白水平、头肾皮质甾醇生成基因（包括类固醇急性调节蛋白（StAR）、细胞色素 P450 侧链裂解酶（P450scc）、11β-羟化酶和黑素皮质素 2 受体（MC2R））的 mRNA 丰度，以及关键的肝脏代谢酶活性。与对照和 10%污水组相比，14 天暴露于污水会显著增加 100%污水组的血浆皮质醇和乳酸水平。与上游对照组相比，污水组的 StAR mRNA 丰度显著升高。与上游对照组相比，100%污水组的肝脏 GR 蛋白水平显著升高，但大脑中 GR 蛋白水平没有显著升高。与其他两组相比，14 天慢性暴露于 100%污水显著降低了肝脏己糖激酶和葡萄糖激酶的活性，但不影响肝糖原含量或磷酸烯醇丙酮酸羧激酶、丙酮酸激酶、乳酸脱氢酶、天冬氨酸转氨酶和丙氨酸转氨酶的活性。将这些鱼暴露于二次急性应激源会引起生理应激反应，包括对照和 10%污水组在应激后 1 小时血浆皮质醇、葡萄糖和乳酸水平显著短暂升高，24 小时后降至应激前水平，但在 100%污水组中，这种保守的应激反应受损。100%污水组鱼在应激后 1 小时的 StAR 和 P450scc mRNA 丰度也显著升高，而所有主要皮质甾醇生成基因的转录丰度在应激后 24 小时均低于对照和 10%污水组。综合来看，14 天暴露于全强度 MWWE 会引起虹鳟的慢性应激反应，并扰乱对急性应激源的保守适应反应。我们的结果表明，经三级处理的 MWWE 对虹鳟应激表现的影响在 90%污水稀释后被消除。
