title: A peak in gh-receptor expression is associated with growth activation in Atlantic salmon vertebrae, while upregulation of igf-I receptor expression is related to increased bone density.
abstract: Growth hormone (GH) and insulin-like growth factor-I (IGF-I) play major roles in the endocrine regulation of fish growth, but their interdependency and mode of action has not been well elucidated. The GH-IGF-I system is essential for normal vertebral growth in mouse, but this has not been studied in fish. To study the interplay between GH, IGF-I, and their receptors, postsmolt Atlantic salmon were studied during spring growth (January-June 2003). From January to June, fish were sampled regularly for plasma and vertebral bone. The vertebra was collected from the same anterior-posterior position. The growth hormone receptor (ghr) (There is no determined nomenclature of salmon genes but we stick to the nomenclature which is consequent for zebrafish, where all gene names are named with small letters and in italic.) expression in the vertebrae peaked in the end of February coinciding with high levels of plasma GH and IGF-I, and an increase of vertebral growth rate. From April to June, plasma IGF-I levels decreased together with ghr expression in the vertebrae, while plasma GH did not decrease. In May and June, expression of the igf-I receptor (igf-Ir) increased 4- to 5-fold, which coincided with an increase in bone density. The changes seen in gene expression of the IGF-I and GH receptors suggest that these hormones are involved in vertebral growth and bone density.
authors.affiliation: Institute of Marine Research, Matre, N-5984 Matredal, Norway. anna.wargelius@imr.no
authors.forename: Anna
authors.initials: A
authors.lastname: Wargelius
authors.forename: Per-Gunnar
authors.initials: PG
authors.lastname: Fjelldal
authors.forename: Susana
authors.initials: S
authors.lastname: Benedet
authors.forename: Tom
authors.initials: T
authors.lastname: Hansen
authors.forename: Björn Thrandur
authors.initials: BT
authors.lastname: Björnsson
authors.forename: Ulla
authors.initials: U
authors.lastname: Nordgarden
mesh_terms: D000818:Animals; D015519:Bone Density / Q000235:genetics*; D006128:Growth / Q000502:physiology*; D013006:Growth Hormone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D011863:Radioimmunoassay; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis* / Q000235:genetics; D011986:Receptors, Somatotropin / Q000096:biosynthesis* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020317:Salmo salar / Q000254:growth & development*; D013131:Spine / Q000254:growth & development*; D015854:Up-Regulation / Q000235:genetics / Q000502:physiology
chemical_list: D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D017526:Receptor, IGF Type 1