Nakkrasae La-iad, Wisetdee Khanitha, Charoenphandhu Narattaphol
Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen, 40002, Thailand,
J Comp Physiol B. 2015 Jul;185(5):527-37. doi: 10.1007/s00360-015-0902-z. Epub 2015 Apr 22.
NaCl-rich rock salt dissolved in natural water source leads to salinity fluctuation that profoundly affects freshwater ecosystem and aquatic fauna. The snakehead (Channa striata) can live in saline water, but the osmoregulatory mechanisms underlying this ability remain unclear. Herein, we found that exposure to salinities ≥ 10‰ NaCl markedly elevated plasma cortisol and glucose levels, and caused muscle dehydration. In a study of time-dependent response after being transferred from fresh water (0‰ NaCl, FW) to salt-dissolved brackish water (10‰ NaCl, SW), FW-SW, cortisol increased rapidly along with elevations of plasma glucose and lactate. Interestingly, plasma cortisol returned to baseline after prolonged exposure, followed by a second peak that probably enhanced the branchial Na(+)/K(+)-ATPase activity. Under SW-FW condition, Na(+)/K(+)-ATPase activity was not altered as compared to SW-adapted fish. In conclusion, salinity change, especially FW-SW, induced a stress response and hence cortisol release in C. striata, which might increase plasma glucose and lactate to energize the branchial Na(+)/K(+)-ATPase.
富含氯化钠的岩盐溶解于天然水源会导致盐度波动，这对淡水生态系统和水生动物产生深远影响。乌鳢（Channa striata）能够生活在咸水中，但其具备这种能力的渗透调节机制仍不清楚。在此，我们发现暴露于盐度≥10‰氯化钠的环境中会显著提高血浆皮质醇和葡萄糖水平，并导致肌肉脱水。在一项从淡水（0‰氯化钠，FW）转移至含盐微咸水（10‰氯化钠，SW），即FW-SW后的时间依赖性反应研究中，皮质醇随着血浆葡萄糖和乳酸水平的升高而迅速增加。有趣的是，长时间暴露后血浆皮质醇恢复至基线水平，随后出现第二个峰值，这可能增强了鳃部Na(+)/K(+)-ATP酶的活性。在SW-FW条件下，与适应SW的鱼类相比，Na(+)/K(+)-ATP酶活性没有改变。总之，盐度变化，尤其是FW-SW，会引发应激反应，从而导致乌鳢释放皮质醇，这可能会增加血浆葡萄糖和乳酸，为鳃部Na(+)/K(+)-ATP酶提供能量。
