Sinha Amit Kumar, Kapotwe Mumba, Dabi Shambel Boki, Montes Caroline da Silva, Shrivastava Jyotsna, Blust Ronny, Boeck Gudrun De
Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Groenenborgerlaan 171, BE-2020 Antwerp, Belgium.
Aquat Toxicol. 2016 Jan;170:129-141. doi: 10.1016/j.aquatox.2015.11.020. Epub 2015 Nov 24.
The main objective of this study was to understand the mode of interaction between waterborne copper (Cu) and high environmental ammonia (HEA) exposure on freshwater fish, and how they influence the toxicity of each other when present together. For this purpose, individual and combined effects of Cu and HEA were examined on selected physiological and ion-regulatory processes and changes at transcript level in the common carp (Cyprinus carpio). Juvenile carp were exposed to 2.6μM Cu (25% of the 96h LC50value) and to 0.65mM ammonia (25% of the 96h LC50value) singly and as a mixture for 12h, 24h, 48h, 84h and 180h. Responses such as ammonia (Jamm) and urea (Jurea) excretion rate, plasma ammonia and urea, plasma ions (Na(+), Cl(-) and K(+)), muscle water content (MWC) as well as branchial Na(+)/K(+)-ATPase (NKA) and H(+)-ATPase activity, and branchial mRNA expression of NKA, H(+)-ATPase, Na(+)/H(+) exchanger (NHE-3) and Rhesus (Rh) glycoproteins were investigated under experimental conditions. Results show that Jamm was inhibited during Cu exposure, while HEA exposed fish were able to increase excretion efficiently. In the combined exposure, Jamm remained at the control levels indicating that Cu and HEA abolished each other's effect. Expression of Rhcg (Rhcg-a and Rhcg-b) mRNA was upregulated during HEA, thereby facilitated ammonia efflux out of gills. On the contrary, Rhcg-a transcript level declined following Cu exposure which might account for Cu induced Jamm inhibition. Likewise, Rhcg-a was also down-regulated in Cu-HEA co-exposed fish whilst a temporary increment was noted for Rhch-b. Fish exposed to HEA displayed pronounced up-regulation in NKA expression and activity and stable plasma ion levels. In both the Cu exposure alone and combined Cu-HEA exposure, ion-osmo homeostasis was adversely affected, exemplified by the significant reduction in plasma [Na(+)] and [Cl(-)], and elevated plasma [K(+)], along with an elevation in MWC. These changes were accompanied by a decline in NKA activity. Gill H(+)-ATPase mRNA levels and activities were not affected by either Cu or HEA or both. Likewise, NHE-3 expression remained unaltered but tended to be numerically higher during HEA exposure. Overall, these data suggest that at equitoxic concentrations (25% of 96h LC50), the individual effect of Cu is more harmful while HEA induces quicker adaptive responses. Our findings also denote a competitive mode of interaction, exemplified by the inhibition of HEA -mediated adaptive responses in the presence of Cu.
本研究的主要目的是了解水体铜（Cu）与高环境氨（HEA）暴露对淡水鱼的相互作用模式，以及它们同时存在时如何相互影响毒性。为此，研究了Cu和HEA对鲤鱼（Cyprinus carpio）选定的生理和离子调节过程以及转录水平变化的单独和联合作用。将幼鱼分别暴露于2.6μM Cu（96小时半数致死浓度（LC50）值的25%）和0.65mM氨（96小时LC50值的25%），以及两者的混合物中，暴露时间为12小时、24小时、48小时、84小时和180小时。在实验条件下，研究了氨（Jamm）和尿素（Jurea）排泄率、血浆氨和尿素、血浆离子（Na(+)、Cl(-)和K(+)）、肌肉含水量（MWC）以及鳃Na(+)/K(+)-ATP酶（NKA）和H(+)-ATP酶活性，以及鳃NKA、H(+)-ATP酶、Na(+)/H(+)交换体（NHE-3）和恒河猴（Rh）糖蛋白的mRNA表达等反应。结果表明，暴露于Cu期间Jamm受到抑制，而暴露于HEA的鱼能够有效增加排泄。在联合暴露中，Jamm保持在对照水平，表明Cu和HEA相互抵消了对方的作用。HEA暴露期间，Rhcg（Rhcg-a和Rhcg-b）mRNA的表达上调，从而促进氨从鳃排出。相反，Cu暴露后Rhcg-a转录水平下降，这可能是Cu诱导Jamm抑制的原因。同样，在Cu-HEA共同暴露的鱼中，Rhcg-a也下调，而Rhch-b有暂时增加。暴露于HEA的鱼NKA表达和活性显著上调，血浆离子水平稳定。在单独Cu暴露和Cu-HEA联合暴露中，离子渗透稳态均受到不利影响，表现为血浆[Na(+)]和[Cl(-)]显著降低，血浆[K(+)]升高，以及MWC升高，同时NKA活性下降。鳃H(+)-ATP酶mRNA水平和活性不受Cu或HEA或两者的影响。同样，NHE-3表达保持不变，但在HEA暴露期间在数值上有升高趋势。总体而言，这些数据表明，在等毒性浓度（96小时LC50的25%）下，Cu的单独作用更有害，而HEA诱导更快的适应性反应。我们的研究结果还表明存在一种竞争相互作用模式，例如在Cu存在下HEA介导的适应性反应受到抑制。
