Nilsen Tom O, Ebbesson Lars O E, Madsen Steffen S, McCormick Stephen D, Andersson Eva, Björnsson Björn Th, Prunet Patrick, Stefansson Sigurd O
Department of Biology, University of Bergen, High Technology Centre, Bergen N-5020, Norway.
J Exp Biol. 2007 Aug;210(Pt 16):2885-96. doi: 10.1242/jeb.002873.
This study examines changes in gill Na(+),K(+)-ATPase (NKA) alpha- and beta-subunit isoforms, Na(+),K(+),2Cl(-) cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR I and II) in anadromous and landlocked strains of Atlantic salmon during parr-smolt transformation, and after seawater (SW) transfer in May/June. Gill NKA activity increased from February through April, May and June among both strains in freshwater (FW), with peak enzyme activity in the landlocked salmon being 50% below that of the anadromous fish in May and June. Gill NKA-alpha1b, -alpha3, -beta(1) and NKCC mRNA levels in anadromous salmon increased transiently, reaching peak levels in smolts in April/May, whereas no similar smolt-related upregulation of these transcripts occurred in juvenile landlocked salmon. Gill NKA-alpha1a mRNA decreased significantly in anadromous salmon from February through June, whereas alpha1a levels in landlocked salmon, after an initial decrease in April, remained significantly higher than those of the anadromous smolts in May and June. Following SW transfer, gill NKA-alpha1b and NKCC mRNA increased in both strains, whereas NKA-alpha1a decreased. Both strains exhibited a transient increase in gill NKA alpha-protein abundance, with peak levels in May. Gill alpha-protein abundance was lower in SW than corresponding FW values in June. Gill NKCC protein abundance increased transiently in anadromous fish, with peak levels in May, whereas a slight increase was observed in landlocked salmon in May, increasing to peak levels in June. Gill CFTR I mRNA levels increased significantly from February to April in both strains, followed by a slight, though not significant increase in May and June. CFTR I mRNA levels were significantly lower in landlocked than anadromous salmon in April/June. Gill CFTR II mRNA levels did not change significantly in either strain. Our findings demonstrates that differential expression of gill NKA-alpha1a, -alpha1b and -alpha3 isoforms may be important for potential functional differences in NKA, both during preparatory development and during salinity adjustments in salmon. Furthermore, landlocked salmon have lost some of the unique preparatory upregulation of gill NKA, NKCC and, to some extent, CFTR anion channel associated with the development of hypo-osmoregulatory ability in anadromous salmon.
本研究检测了溯河洄游型和陆封型大西洋鲑在幼鲑-成鲑转化过程中以及5月/6月转入海水（SW）后，鳃中钠钾ATP酶（NKA）α和β亚基同工型、钠钾氯共转运体（NKCC）和囊性纤维化跨膜传导调节因子（CFTR I和II）的变化。在淡水中，从2月到4月、5月和6月，两种鲑鱼鳃中的NKA活性均升高，5月和6月陆封型鲑鱼的酶活性峰值比溯河洄游型鱼低50%。溯河洄游型鲑鱼鳃中NKA-α1b、-α3、-β(1)和NKCC的mRNA水平短暂升高，在4月/5月的成鲑中达到峰值水平，而幼体陆封型鲑鱼中未出现与成鲑相关的这些转录本的上调。溯河洄游型鲑鱼鳃中NKA-α1a的mRNA从2月到6月显著下降，而陆封型鲑鱼中α1a水平在4月初始下降后，在5月和6月仍显著高于溯河洄游型成鲑。转入海水后，两种鲑鱼鳃中NKA-α1b和NKCC的mRNA均增加，而NKA-α1a下降。两种鲑鱼鳃中NKAα蛋白丰度均短暂增加，5月达到峰值水平。6月时，海水中鳃α蛋白丰度低于相应淡水中的值。溯河洄游型鱼鳃中NKCC蛋白丰度短暂增加，5月达到峰值水平，而陆封型鲑鱼5月略有增加，6月增加到峰值水平。两种鲑鱼鳃中CFTR I的mRNA水平从2月到4月显著增加，随后在5月和6月略有增加，但不显著。4月/6月陆封型鲑鱼鳃中CFTR I的mRNA水平显著低于溯河洄游型鲑鱼。两种鲑鱼鳃中CFTR II的mRNA水平均无显著变化。我们的研究结果表明，鳃中NKA-α1a、-α1b和-α3同工型的差异表达可能对鲑鱼在准备发育过程中和盐度调节过程中NKA的潜在功能差异很重要。此外，陆封型鲑鱼已经失去了一些与溯河洄游型鲑鱼低渗调节能力发育相关鳃NKA、NKCC以及在一定程度上CFTR阴离子通道的独特准备上调。
