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Seawater tolerance and gene expression in two strains of Atlantic salmon smolts

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The seawater tolerance of Atlantic salmon (Salmo salar) smolts reared under identical hatchery conditions was assessed in two Norwegian strains: AquaGen and Imsa. Plasma ion levels were disrupted in both strains following seawater exposure, but these disruptions were more profound in the AquaGen fish. To investigate the mechanisms underlying these differences, we measured gill Na+,K+-adenosine triphosphatase (ATPase) activity and mRNA levels of Na+,K+-ATPase α-subunit and two isoforms of the cystic fibrosis transmembrane conductance regulator (CFTR). Gill Na+,K+-ATPase activity rose significantly in both strains following seawater exposure. Both Na+,K+-ATPase α-subunit and CFTR I mRNA levels were significantly elevated for the entire 2-week period following seawater exposure, whereas CFTR II levels were transiently elevated during the first 24 h only. There were no differences in enzyme activity or gene expression between strains, with the exception of CFTR II, which was significantly lower in the Imsa strain 2 weeks following seawater exposure. This suggests that although changes in mRNA and protein expression for these genes are associated with seawater transfer, they are not the basis of observed physiological differences between strains.

Nous avons étudié la tolérance à l'eau de mer de saumoneaux élevés en conditions identiques de pisciculture chez deux lignées norvégiennes du saumon de l'Atlantique (Salmo salar), AquaGen et Imsa. Une exposition à l'eau de mer perturbe les concentrations des ions du plasma chez les deux lignées, mais plus fortement chez les poissons AquaGen. Pour étudier les mécanismes qui expliquent ces différences, nous avons mesuré l'activité de la Na+,K+-adénosine triphosphatase (ATPase) des branchies et les quantités d'ARNm de la sous-unité α de la Na+,K+-ATPase et de deux isoformes du régulateur du transport transmembranaire de la fibrose kystique (CFTR). L'activité de la Na+,K+-ATPase des branchies s'accroît de façon significative chez les deux lignées après une exposition à l'eau de mer. Les quantités d'ARNm augmentent significativement tant chez la sous-unité α de la Na+,K+-ATPase que chez CFTR I pendant les deux semaines complètes qui suivent l'exposition à l'eau de mer; chez CFTR II, l'augmentation n'est que temporaire pendant les 24 premières heures. Il n'y a pas de différences dans l'activité enzymatique ou l'expression des gènes entre les deux lignées, excepté chez CFTR II de la lignée Imsa dont l'expression est plus faible deux semaines après l'exposition. Il appert donc que, bien que des changements dans les quantités d'ARNm et dans l'expression de protéines de ces gènes accompagnent le transfert à l'eau de mer, ils ne sont pas responsables des différences physiologiques observées entre les deux lignées.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2002-01-01

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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