Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Amazonian Research, Manaus, AM, Brazil.
São Paulo State University (UNESP), Institute of Biosciences, Campus do Litoral Paulista, Pça Infante Dom Henrique s/no, Parque Bitaru, São Vicente, SP, 11330-900, Brazil.
Environ Sci Pollut Res Int. 2018 Jun;25(18):18027-18037. doi: 10.1007/s11356-018-2064-5. Epub 2018 Apr 24.
Formation water (FoW) is a by-product from oil and gas production and usually has high concentrations of soluble salts and metals. Calcium (Ca) and magnesium (Mg) have been shown to reduce the toxicity of metals to aquatic animals, and previous study showed that high waterborne Ca exerts mild effect against disturbances on Na regulation in Amazonian armored catfish tamoatá (Hoplosternum littorale) acutely exposed to high Fe, Mn, and Ba levels. Here, we hypothesized that high Mg levels might also reduce the toxic effects of these metals on Na regulation of tamoatá. The exposure to 5% FoW promoted an increase in Na uptake and a rapid accumulation of Na in all tissues analyzed (kidney<plasma<gills<carcass<liver), besides increasing the branchial activity of both NKA and v-type H-ATPase in fish. High waterborne Mg lowered Na efflux rates and markedly inhibited Na uptake, and also reduced both NKA activity and newly Na accumulation in gills of fish. High Fe levels increased Na net losses and inhibited Na uptake in tamoatá. The diffusive Na losses and the newly accumulated Na in gills were reduced in fish exposed to high Mn and Ba. High waterborne Ba also inhibited NKA in gills, while both high Mn and Ba inhibited v-type H-ATPase in kidney of tamoatá. High Mg did not lessen the toxic effect of Fe on Na net fluxes, and reduced even more Na uptake and the newly Na accumulation in gills and plasma, and did not prevent the inhibition of both NKA and v-type H-ATPases in kidney. Furthermore, Mg did not attenuate the effect of Mn on inhibition Na uptake, keeping the activity of v-type H-ATPase in kidney significantly lowered. High Mg levels mildly attenuated the effects of Ba in Na balance by increasing the new accumulation of Na in liver, and restore the activity of both NKA and v-type H-ATPase in gills of tamoatá. Overall, high waterborne Mg does not have a strong contribution to, or have only minor effects, in protecting tamoatá against disruptions in Na regulation mediated by high Fe, Mn, and Ba levels.
地层水（FoW）是石油和天然气生产的副产品，通常含有高浓度的可溶性盐和金属。钙（Ca）和镁（Mg）已被证明可以降低金属对水生动物的毒性，先前的研究表明，高水溶性 Ca 对亚马逊 armored 鲶鱼（Hoplosternum littorale）在急性暴露于高 Fe、Mn 和 Ba 水平时对 Na 调节的干扰具有温和的影响。在这里，我们假设高 Mg 水平也可能降低这些金属对 Na 调节的毒性作用。暴露于 5% FoW 会促进 Na 摄取的增加，并使所有分析组织中的 Na 快速积累（肾脏<血浆<鳃<体腔<肝脏），同时增加鱼类鳃部 NKA 和 v 型 H-ATPase 的活性。高水溶性 Mg 降低了 Na 外排率，并显著抑制了 Na 的摄取，还降低了鱼类鳃部 NKA 的活性和新的 Na 积累。高 Fe 水平增加了 tamoatá 的 Na 净损失并抑制了 Na 的摄取。高 Mn 和 Ba 暴露的鱼的鳃部扩散性 Na 损失和新积累的 Na 减少。高水溶性 Ba 还抑制了鱼类鳃部的 NKA，而高 Mn 和 Ba 均抑制了 tamoatá 肾脏中的 v 型 H-ATPase。高 Mg 并没有减轻 Fe 对 Na 净通量的毒性作用，反而更多地减少了 Na 的摄取和新的在鳃部和血浆中的积累，并不能防止 NKA 和 v 型 H-ATPase 在肾脏中的抑制作用。此外，Mg 并没有减轻 Mn 对抑制 Na 摄取的影响，使肾脏中 v 型 H-ATPase 的活性显著降低。高 Mg 水平通过增加肝脏中新积累的 Na，轻微减轻了 Ba 在 Na 平衡中的作用，并恢复了 tamoatá 鳃部的 NKA 和 v 型 H-ATPase 的活性。总的来说，高水溶性 Mg 并没有对高 Fe、Mn 和 Ba 水平引起的 Na 调节紊乱产生强烈的保护作用，或者只有轻微的影响。
