Shrimpton J M, Patterson D A, Richards J G, Cooke S J, Schulte P M, Hinch S G, Farrell A P
Ecosystem Science and Management Program, University of Northern British Columbia, Prince George, BC, V2N 4Z9, Canada.
J Exp Biol. 2005 Nov;208(Pt 21):4069-78. doi: 10.1242/jeb.01871.
We present the first data on changes in ionoregulatory physiology of maturing, migratory adult sockeye salmon Oncorhynchus nerka. Fraser River sockeye were intercepted in the ocean as far away as the Queen Charlotte Islands (approximately 850 km from the Fraser River) and during freshwater migration to the spawning grounds; for some populations this was a distance of over 700 km. Sockeye migrating in seawater toward the mouth of the Fraser River and upriver to spawning grounds showed a decline in gill Na+,K+-ATPase activity. As a result, gill Na+,K+-ATPase activity of fish arriving at the spawning grounds was significantly lower than values obtained from fish captured before entry into freshwater. Plasma osmolality and chloride levels also showed significant decreases from seawater values during the freshwater migration to spawning areas. Movement from seawater to freshwater increased mRNA expression of a freshwater-specific Na+,K+-ATPase isoform (alpha1a) while having no effect on the seawater-specific isoform (alpha1b). In addition, gill Na+,K+-ATPase activity generally increased in active spawners compared with unspawned fish on the spawning grounds and this was associated with a marked increase in Na+,K+-ATPase alpha1b mRNA. Increases in gill Na+,K+-ATPase activities observed in spawners suggests that the fish may be attempting to compensate for the osmotic perturbation associated with the decline in plasma chloride concentration and osmolality.
我们展示了关于成熟洄游成年红大马哈鱼（Oncorhynchus nerka）离子调节生理学变化的首批数据。弗雷泽河红大马哈鱼在海洋中被截获，最远可达夏洛特皇后群岛（距弗雷泽河约850公里），以及在向产卵地的淡水洄游期间；对于一些种群来说，这一距离超过700公里。向弗雷泽河河口和上游产卵地洄游的海水环境中的红大马哈鱼，其鳃部钠钾ATP酶活性下降。因此，到达产卵地的鱼的鳃部钠钾ATP酶活性显著低于进入淡水之前捕获的鱼的测量值。在向产卵区的淡水洄游过程中，血浆渗透压和氯离子水平也较海水环境中的值显著降低。从海水环境转移到淡水环境会增加一种淡水特异性钠钾ATP酶同工型（α1a）的mRNA表达，而对海水特异性同工型（α1b）没有影响。此外，与产卵场中未产卵的鱼相比，正在产卵的鱼的鳃部钠钾ATP酶活性总体上有所增加，这与钠钾ATP酶α1b的mRNA显著增加有关。在产卵鱼中观察到的鳃部钠钾ATP酶活性增加表明，鱼可能在试图补偿与血浆氯离子浓度和渗透压下降相关的渗透扰动。
