Appearance of insulin and insulin-like growth factor-I (IGF-I) receptors throughout the ontogeny of brown trout (Salmo trutta fario).
Insulin and IGF-I receptors were characterized in glycoprotein fractions prepared by affinity chromatography from different developmental stages of brown trout. The specificity of insulin and IGF-I binding was demonstrated by crossed-competition assays: unlabelled insulin displaced bound radiolabelled insulin at concentrations 45-fold lower than unlabelled IGF-I, whilst unlabelled IGF-I displaced bound radiolabelled IGF-I at concentrations 2,000-fold lower than unlabelled insulin. The affinity of these receptors did not change significantly during trout development. Insulin-specific binding was detectable 3 weeks after spawning, after which it increased to a maximum in fry weighing 0.4 g, and decreased progressively to adult levels. IGF-I specific binding was detectable in newly laid eggs and increased to a maximum during organogenesis in eyed eggs. It then decreased progressively during subsequent stages of development to adult levels. The apparent molecular weight (Mr) of the alpha-subunit of brown trout insulin and IGF-I receptors was smaller than that of the alpha-subunit of the rat insulin receptor. Receptor tyrosine kinase activity was stimulated in a dose-dependent manner by insulin and IGF-I. Insulin and IGF-I stimulated tyrosine kinase activity and reached a maximum of 201 +/- 17.6 and 240 +/- 29.6% of basal phosphorylation, respectively.
Maestro
M A
MA
Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Spain.
Méndez
E
E
Bayraktaroglu
E
E
Baños
N
N
Gutiérrez
J
J
D000818:Animals; D003432:Cross-Linking Reagents / Q000737:chemistry; D004625:Embryo, Nonmammalian; D007328:Insulin / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008970:Molecular Weight; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000737:chemistry / Q000378:metabolism; D011972:Receptor, Insulin / Q000737:chemistry / Q000378:metabolism; D014337:Trout / Q000196:embryology / Q000254:growth & development*
D003432:Cross-Linking Reagents; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin