title: Expression of insulin-like growth factor I gene in osmoregulatory organs during seawater adaptation of the salmonid fish: possible mode of osmoregulatory action of growth hormone.
abstract: Growth hormone has been shown to contribute to seawater adaptation of salmonid fishes. The growth influence of growth hormone is mediated largely by hepatic production of insulin-like growth factor I (IGF-I). To study the growth hormone-IGF-I axis in osmoregulation, we measured IGF-I mRNA in the liver, gill, and body kidney from rainbow trout by Northern analysis. The levels of IGF-I mRNA in all tissues increased significantly after injection of growth hormone. Transfer of trout from fresh water to 80% seawater evoked an increase in plasma growth hormone after 1 day. IGF-I mRNA was not altered significantly in the liver, but it was increased in the gill and body kidney after 1 and 8 days, respectively. These observations indicate that the IGF-I gene is expressed differently among these organs during seawater adaptation. Growth hormone may stimulate hypoosmoregulatory ability by inducing local expression of IGF-I in osmoregulatory organs, although the possibility that IGF-I expression might occur in part independently of growth hormone during seawater adaptation cannot be excluded.
authors.affiliation: Ocean Research Institute, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sakamoto
authors.forename: T
authors.initials: T
authors.lastname: Hirano
mesh_terms: D000818:Animals; D015870:Gene Expression / Q000187:drug effects; D005880:Gills / Q000502:physiology; D013006:Growth Hormone / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007668:Kidney / Q000502:physiology; D008099:Liver / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D012623:Seawater; D014337:Trout / Q000235:genetics*; D014882:Water-Electrolyte Balance
chemical_list: D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone