title: Hepatic insulin-like growth-factor binding protein (igfbp) responses to food restriction in Atlantic salmon smolts.
abstract: The growth hormone (Gh)/insulin-like growth-factor (Igf) system plays a central role in the regulation of growth in fishes. However, the roles of Igf binding proteins (Igfbps) in coordinating responses to food availability are unresolved, especially in anadromous fishes preparing for seaward migration. We assayed plasma Gh, Igf1, thyroid hormones and cortisol along with igfbp mRNA levels in fasted and fed Atlantic salmon (Salmo salar). Fish were fasted for 3 or 10days near the peak of smoltification (late April to early May). Fasting reduced plasma glucose by 3days and condition factor by 10days. Plasma Gh, cortisol, and thyroxine (T4) were not altered in response to fasting, whereas Igf1 and 3,5,3'-triiodo-l-thyronine (T3) were slightly higher and lower than controls, respectively. Hepatic igfbp1b1, -1b2, -2a, -2b1 and -2b2 mRNA levels were not responsive to fasting, but there were marked increases in igfbp1a1 following 3 and 10days of fasting. Fasting did not alter hepatic igf1 or igf2; however, muscle igf1 was diminished by 10days of fasting. There were no signs that fasting compromised branchial ionoregulatory functions, as indicated by unchanged Na(+)/K(+)-ATPase activity and ion pump/transporter mRNA levels. We conclude that dynamic hepatic igfbp1a1 and muscle igf1 expression participate in the modulation of Gh/Igf signaling in smolts undergoing catabolism.
authors.affiliation: Department of Biology, Skidmore College, 815 N. Broadway, Saratoga Springs, NY 12866, USA. Electronic address: jbreves@skidmore.edu.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Breves
authors.affiliation: Department of Biology, Skidmore College, 815 N. Broadway, Saratoga Springs, NY 12866, USA.
authors.forename: Silas K
authors.initials: SK
authors.lastname: Phipps-Costin
authors.affiliation: Department of Biology, Skidmore College, 815 N. Broadway, Saratoga Springs, NY 12866, USA.
authors.forename: Chelsea K
authors.initials: CK
authors.lastname: Fujimoto
authors.affiliation: Fish Endocrinology Laboratory, Department of Biological and Environmental Sciences, University of Gothenburg, Box 463, SE-40530 Göteborg, Sweden.
authors.forename: Ingibjörg E
authors.initials: IE
authors.lastname: Einarsdottir
authors.affiliation: USGS, Conte Anadromous Fish Research Center, P.O. Box 796, One Migratory Way, Turners Falls, MA 01376, USA.
authors.forename: Amy M
authors.initials: AM
authors.lastname: Regish
authors.affiliation: Fish Endocrinology Laboratory, Department of Biological and Environmental Sciences, University of Gothenburg, Box 463, SE-40530 Göteborg, Sweden.
authors.forename: Björn Thrandur
authors.initials: BT
authors.lastname: Björnsson
authors.affiliation: USGS, Conte Anadromous Fish Research Center, P.O. Box 796, One Migratory Way, Turners Falls, MA 01376, USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: McCormick
mesh_terms: D025041:Animal Migration / Q000502:physiology; D000818:Animals; D031204:Caloric Restriction / Q000662:veterinary; D005215:Fasting / Q000502:physiology; D005508:Food Deprivation / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D061385:Insulins / Q000378:metabolism; D008018:Life Cycle Stages / Q000502:physiology*; D008099:Liver / Q000378:metabolism*; D020317:Salmo salar / Q000254:growth & development* / Q000378:metabolism*; D055049:Salt Tolerance / Q000502:physiology; D012621:Seasons
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D061385:Insulins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone
keywords: Atlantic salmon; Binding proteins; Fasting; Growth hormone; Insulin-like growth-factor; Liver