Department of Biology, University of Bergen, Bergen High Technology Centre, Bergen, Norway.
Aquat Toxicol. 2010 May 5;97(3):250-9. doi: 10.1016/j.aquatox.2009.12.001. Epub 2009 Dec 4.
Na(+), K(+)-ATPase (NKA) is involved, through its role as a major driving force for electrochemical gradients, in a range of transmembrane transport processes. Maintenance of homeostasis in anadromous salmonids requires modulation of several gill ion secretory proteins as part of the preparatory adaptation and acclimation to marine life. Atlantic salmon smolts were exposed to combinations of low pH and inorganic aluminum (acid/Al(i)) in freshwater (FW) and were then transferred to seawater (SW) for studies of post-smolt performance. Gill mRNA levels of four NKA-alpha isoforms (alpha1a, alpha1b, alpha1c and alpha3) of the catalytic NKA subunit and NKA enzyme activity were measured. Moderate acid/Al treatment (MOD, pH 5.9+/-0.3, 15+/-9microgl(-1)Al(i)) prevented the FW preparatory increase in NKA activity observed in control (CON, pH 6.9+/-0.1, 8+/-3microgl(-1)Al(i)) smolts, while high acid/Al treatment (SEV, pH 5.6+/-0.2, 30+/-7microgl(-1)Al(i)) caused a rapid and persistent reduction in NKA activity. Correspondingly, a 3.3-fold increase in plasma glucose levels in the SEV groups concurrent with a decrease in plasma chloride levels suggest that acid/Al exposed fish were stressed and experienced problems maintaining ion homeostasis. Gill NKA activities in acid/Al exposed groups were re-established after 28 days in SW. Both long (9 days) and short-term (2.5 days) treatments had significant impact on isoform-specific Na(+), K(+)-ATPase alpha-subunit mRNA abundance in the FW period. Acid/Al exposed groups lacked the preparatory increases in all NKA-alpha isoform mRNA levels seen in the CON group, except for alpha1a. In contrast to the other isoforms measured, alpha1a mRNA abundance decreased sharply upon SW transfer, supporting the hypothesis of isozyme shifting as a mechanism of altering the gill from an ion absorbing to an ion excreting tissue during smoltification and SW exposure. Adult return rates to the Imsa river were significantly reduced both in short-term (78% of controls) and long-term (55% of controls) acid/Al exposures, emphasising the physiological and ecological consequences of acid/Al exposure during smoltification.
钠钾-ATP 酶（NKA）通过其作为电化学梯度的主要驱动力的作用，参与了一系列跨膜转运过程。洄游性鲑鱼的体内平衡维持需要调节几种鳃离子分泌蛋白，作为对海洋生活的预备适应和适应的一部分。大西洋鲑鱼苗在淡水（FW）中暴露于低 pH 值和无机铝（酸/Al(i)）的组合中，然后转移到海水中（SW），以研究后期的表现。测量了催化 NKA 亚基的四个 NKA-α同工型（alpha1a、alpha1b、alpha1c 和 alpha3）和 NKA 酶活性的鳃 mRNA 水平。适度酸/Al 处理（MOD，pH5.9+/-0.3，15+/-9microgl(-1)Al(i)）阻止了对照（CON，pH6.9+/-0.1，8+/-3microgl(-1)Al(i)）鱼苗在 FW 预备期观察到的 NKA 活性增加，而高酸/Al 处理（SEV，pH5.6+/-0.2，30+/-7microgl(-1)Al(i)）导致 NKA 活性迅速和持续降低。相应地，SEV 组血浆葡萄糖水平升高了 3.3 倍，同时血浆氯离子水平降低，表明酸/Al 暴露的鱼受到压力，离子稳态维持出现问题。暴露于酸/Al 的鱼在 SW 中 28 天后恢复了鳃 NKA 活性。在 FW 期，长期（9 天）和短期（2.5 天）处理都对同工型特异性 Na(+), K(+)-ATPase α-亚基 mRNA 丰度有显著影响。暴露于酸/Al 的鱼群缺乏在对照（CON）组中观察到的所有 NKA-α同工型 mRNA 水平的预备性增加，除了 alpha1a。与所测量的其他同工型不同，alpha1a 的 mRNA 丰度在转移到 SW 后急剧下降，支持同工型转换作为在变态和 SW 暴露期间将鳃从离子吸收组织转变为离子排泄组织的机制的假说。在短期（对照的 78%）和长期（对照的 55%）酸/Al 暴露中，返回 Imsa 河的成年鱼的返回率都显著降低，强调了变态期间酸/Al 暴露对生理和生态的影响。
