Interactive effects of cortisol treatment and ambient seawater challenge on gill Na+,K+-ATPase and CFTR expression in two strains of Atlantic salmon smolts

Singer, T. D.; Finstad, B.; McCormick, S. D.; Wiseman, S. B.; Schulte, P. M.; McKinley, R. S.

Abstract:

During peak smoltification, the interactive effects of cortisol and ambient seawater challenge were compared in two strains of Atlantic salmon (Salmo salar) smolts: a domesticated strain, AquaGen and a native River Imsa strain. Tissue and blood samples were taken from untreated fish on 20 May. Fish were then transferred to experimental tanks, allowed to recover for 24 h and cortisol (50 mg kg body mass-1), dissolved in vegetable oil, or vegetable oil alone (sham) was implanted. Samples were taken 5 days post implantation. Fish were then exposed to 24 h ambient seawater challenge (FW-SW) or freshwater to freshwater replacement (FW-FW) and sampled as before. Sham implantation had no significant impact on any of the measured parameters. Cortisol implantation significantly elevated plasma cortisol in FW-FW Imsa smolts, while no effect was observed in FW-SW Imsa smolts. Cortisol implantation had no effect on the plasma cortisol levels of AquaGen smolts regardless of FW-SW challenge. Increased plasma cortisol corresponded with significantly higher plasma glucose levels in FW-FW Imsa smolts. Plasma Na+ and Cl- levels were not affected by cortisol implantation but were significantly increased in FW-SW smolts of both strains. Gill Na+,K+-ATPase activity increased in response to cortisol implantation in only FW-FW smolts but not FW-SW smolts. Gill Na+,K+-ATPase ??-subunit mRNA levels were not affected by strain, cortisol injection or transfer protocol, while both CFTR I and CFTR II mRNA levels were significantly higher in AquaGen versus Imsa smolts regardless of treatment. CFTR I mRNA was elevated following cortisol implantation in FW-FW smolts from both strains suggesting CFTR I expression is under the control of cortisol. These findings also suggest that plasma cortisol levels are regulated differently between strains and that cortisol implantation and ambient FW-SW challenge interact, interfering with the individual effects of each of these factors. ?? 2003 Published by Elsevier Science B.V.

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Article

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70026076

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Singer, T. D.; Finstad, B.; McCormick, S. D.; Wiseman, S. B.; Schulte, P. M.; McKinley, R. S.

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1-4

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English

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Aquaculture

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Interactive effects of cortisol treatment and ambient seawater challenge on gill Na+,K+-ATPase and CFTR expression in two strains of Atlantic salmon smolts; 2003; Article; Journal; Aquaculture; Singer, T. D.; Finstad, B.; McCormick, S. D.; Wiseman, S. B.; Schulte, P. M.; McKinley, R. S.