Variation in salinity tolerance, gill Na+/K+-ATPase, Na+/K+/2Cl- cotransporter and mitochondria-rich cell distribution in three salmonids Salvelinus namaycush, Salvelinus fontinalis and Salmo salar
Variation in salinity tolerance, gill Na+/K+-ATPase, Na+/K+/2Cl- cotransporter and mitochondria-rich cell distribution in three salmonids Salvelinus namaycush, Salvelinus fontinalis and Salmo salar
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DOI：
10.1242/jeb.002030
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发表时间：
2007-03-15
影响因子：
2.8
通讯作者：
McCormick, Stephen D.
中科院分区：
文献类型：
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作者：
Hiroi, Junya;McCormick, Stephen D.
本研究比较了三种鲑科鱼类的海水耐受性、鳃Na+/K+- atp酶和Na+/K+/2Cl（-）共转运体（NKCC）丰度和富线粒体细胞（MRC）形态，即湖鳟Salvelinus namaycush、溪鳟Salvelinus fontinalis和大西洋鲑Salmo salar。它们直接从0 p.p.t（千分之一淡水）转移到30 p.p.t海水，或者每隔一周逐渐从0转移到10、20和30 p.t，并在30 p.t中保持3周。湖鳟、溪鳟和大西洋鲑鱼直接转移后的成活率分别为80%、50%和100%，逐渐转移后的成活率分别为80%、100%和100%。湖鳟鱼血浆Na+、K+和Cl-浓度在直接转移和逐渐转移过程中均迅速升高，并在30 p.p.t.时保持较高水平，而溪鳟鱼血浆Na+、K+和Cl-浓度在直接转移后出现短暂升高，但在逐渐转移过程中变化不显著。在大西洋鲑鱼幼崽中，等离子体离子在直接和逐渐转移中只发生了微小的变化。这些结果表明，湖鳟保留了一定程度的全咸度，而溪鳟的全咸度介于湖鳟和大西洋鲑鱼幼崽之间。湖鳟和溪鳟的鳃Na+/K+- atp酶活性在海水中升高，而大西洋鲑鱼幼鱼的鳃Na+/K+- atp酶活性在淡水中已经上调，并在海水暴露后保持较高水平。NKCC丰度与鳃Na+/K+- atp酶活性同步上调。抗na +/K+- atp酶α亚基和抗nkcc的免疫细胞化学表明，这两种离子转运体在鳃核磁共振细胞的基底外侧膜上共定位。在淡水养殖的3种植物中，MRCs免疫阳性分布在初级细丝和次级薄片上；在转移到海水后，湖鳟和溪鳟的这种模式没有改变，但大西洋鲑鱼的片层状MRCs消失了。以往对几种硬骨鱼的研究表明，丝状和片状的MRCs分别参与了海水和淡水的驯化。然而，我们对湖鳟和溪鳟的研究结果表明，片层状MRCs在海水驯化过程中也可能起作用。
We compared seawater tolerance, gill Na+/K+-ATPase and Na+/K+/2Cl(-) cotransporter (NKCC) abundance, and mitochondria-rich cell (MRC) morphology of three salmonids, lake trout Salvelinus namaycush, brook trout Salvelinus fontinalis and Atlantic salmon Salmo salar. They were transferred directly from 0 p.p.t. (parts per thousand; freshwater) to 30 p.p.t. seawater, or transferred gradually from 0 to 10, 20 and 30 p.p.t. at 1-week intervals and kept in 30 p.p.t. for 3 weeks. The survival rates of lake trout, brook trout and Atlantic salmon were 80%, 50% and 100% following direct transfer, and 80%, 100% and 100% during gradual transfer, respectively. Plasma Na+, K+ and Cl- concentrations in surviving lake trout increased rapidly and remained at high levels in 30 p.p.t. of both direct and gradual transfer, whereas those in brook trout showed a transient increase following direct transfer but did not change significantly during gradual transfer. Only minor changes in plasma ions were observed in Atlantic salmon smolts in both direct and gradual transfer. These results suggest that lake trout retains some degree of euryhalinity and that brook trout possesses intermediate euryhalinity between lake trout and Atlantic salmon smolts. Gill Na+/K+-ATPase activity of lake trout and brook trout increased in seawater, whereas that of Atlantic salmon smolts was already upregulated in freshwater and remained high after seawater exposure. NKCC abundance was upregulated in parallel with gill Na+/K+-ATPase activity in each species. Immunocytochemistry with anti-Na+/K+-ATPase alpha-subunit and anti-NKCC revealed that the two ion transporters were colocalized on the basolateral membrane of gill MRCs. Immunopositive MRCs were distributed on both primary filaments and secondary lamellae in all three species kept in freshwater; following transfer to seawater this pattern did not change in lake trout and brook trout but lamellar MRCs disappeared in Atlantic salmon. Previous studies on several teleost species have suggested that filament and lamellar MRCs would be involved in seawater and freshwater acclimation, respectively. However, our results in lake trout and brook trout suggest that lamellar MRCs could be also functional during seawater acclimation.