title: Effects of growth hormone and insulin-like growth factor I on salinity tolerance and gill Na+, K+-ATPase in Atlantic salmon (Salmo salar): interaction with cortisol.
abstract: The potential roles of growth hormone (GH) and insulin-like growth factor I (IGF-I) in seawater (SW) acclimation of juvenile Atlantic salmon (Salmo salar) were examined. Compared to controls, fish in 12 ppt seawater given one or three injections (2-6 days) of GH (ovine, 0.2 microgram.g-1) or IGF-I (recombinant bovine, 0.05-0.2 microgram.g-1) had significantly greater salinity tolerance as judged by lower plasma sodium, osmolality, and muscle moisture content following transfer to 34 ppt. Single injections of GH and IGF-I in fish in fresh water failed to improve salinity tolerance following transfer to 25 ppt SW. Treatment of fish in 12 ppt with GH or IGF-I for 2-6 days did not increase gill Na+, K(+)-ATPase activity, but treatment with GH prevented decreases in gill Na+, K(+)-ATPase activity that occurred in controls following transfer to 34 ppt seawater. Fish in fresh water administered GH by implants (5.0 microgram.g-1) or osmotic minipumps (0.5 micrograms.g-1 day-1) for 7-14 days had greater gill Na+, K(+)-ATPase activity and salinity tolerance than controls. IGF-I administered by implants (0.5-1.0 microgram.g-1) or osmotic minipumps (0.1 microgram.g-1 day-1) for 4-14 days did not increase salinity tolerance or gill Na+, K(+)-ATPase activity. Cortisol implants (50 micrograms.g-1) also increased gill Na+, K(+)-ATPase activity and salinity tolerance after 14 days, and in combination with GH had a synergistic effect, Although IGF-I and cortisol implants had no significant effect after 7 days, in combination they significantly increased gill Na+, K(+)-ATPase activity. The results indicate that GH and cortisol can increase salinity tolerance and gill Na+, K(+)-ATPase activity of Atlantic salmon and together act in synergy. Although IGF-I can increase salinity tolerance in short-term treatments (2-6 days) in 12 ppt, it is less effective than GH in increasing salinity tolerance and gill Na+, K(+)-ATPase activity in long-term treatments (7-14 days) and in interacting with cortisol.
authors.affiliation: Anadromous Fish Research Center, National Biological Service, Turners Falls, Massachusetts 01376, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: McCormick
mesh_terms: D000064:Acclimatization / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004357:Drug Synergism; D005618:Fresh Water / Q000032:analysis; D005880:Gills / Q000187:drug effects / Q000201:enzymology*; D013006:Growth Hormone / Q000494:pharmacology*; D006854:Hydrocortisone / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009994:Osmolar Concentration; D012474:Salmon / Q000378:metabolism*; D012623:Seawater / Q000032:analysis; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone