Department of Marine Science, Marine Science Institutem, University of Texas at Austin, Port Aransas, TX, 78373, USA.
J Comp Physiol B. 2021 Jul;191(4):731-740. doi: 10.1007/s00360-021-01356-y. Epub 2021 Apr 12.
Prolonged drought and freshwater diversion are making periods of hypersalinity more common in coastal ecosystems. This is especially true in the Laguna Madre system along the Texas coast where salinities can exceed 60 g/kg. As such, the ability to tolerate hypersalinity is critical to the success of endemic species, such as the commercially important red drum (Sciaenops ocellatus). This study evaluated acclimation of red drum to hypersalinity (60 g/kg) using a direct transfer protocol. Hypersalinity exposure resulted in significant impacts on plasma osmolality and muscle water in the first 24 h, but returned to control values coincident with a significant increase in intestinal water volume. Hypersalinity acclimation resulted in significant branchial and intestinal plasticity. The gill showed significant elevated nka α1a, nkcc1 and vha (B subunit) mRNA abundance, as well as NKA enzyme activity. The posterior intestine showed a stronger plasticity signal than the anterior intestine, which included a 12-fold increase in nkcc2 mRNA abundance and significant increases in NKA and VHA enzyme activity. These changes were corroborated by a significant threefold increase in bumetanide-sensitive absorptive short circuit current. These data suggest that the dynamic regulation of NKCC2-mediated intestinal water absorption is an important compliment to HCO-mediated water absorption during hypersalinity exposure and acclimation.
长时间的干旱和淡水转移使得沿海生态系统中出现高盐度的时期更为常见。在德克萨斯州海岸的拉古纳马德拉系统中，这种情况尤其如此，那里的盐度可以超过 60g/kg。因此，能够耐受高盐度对于本地物种的成功至关重要，例如具有商业重要性的红鼓鱼（Sciaenops ocellatus）。本研究使用直接转移方案评估了红鼓鱼对高盐度（60g/kg）的适应能力。高盐度暴露在最初的 24 小时内对血浆渗透压和肌肉水分产生了显著影响，但随着肠道水分体积的显著增加，又恢复到对照值。高盐度适应导致鳃和肠道发生显著的可塑性变化。鳃显示出 nka α1a、nkcc1 和 vha（B 亚基）mRNA 丰度以及 NKA 酶活性的显著升高。后肠比前肠显示出更强的可塑性信号，nkcc2 mRNA 丰度增加了 12 倍，并且 NKA 和 VHA 酶活性也显著增加。这些变化与布美他尼敏感的吸收短路电流显著增加三倍相吻合。这些数据表明，NKCC2 介导的肠道水分吸收的动态调节是在高盐度暴露和适应过程中 HCO3 介导的水分吸收的重要补充。
