IGF-I binding in primary culture of muscle cells of rainbow trout: changes during in vitro development.
To characterize and study the variations of IGF-I binding during the development of trout muscle cells, in vitro experiments were conducted using myocyte cultures, and IGF-I binding assays were performed in three stages of cell development: mononuclear cells (day 1), small myotubes (day 4), and large myotubes (day 10). Binding experiments were done by incubating cells with IGF-I for 12 h at 4 degrees C. Specific IGF-I binding increased with the concentration of labeled IGF-I and reached a plateau at 32 pM. The displacement of cold human and trout IGF-I showed a very similar curve (EC(50) = 1.19 +/- 0.05 and 0.95 +/- 0.05 nM, respectively). IGF binding proteins did not interfere significantly because displacement of labeled IGF-I by either cold trout recombinant IGF-I or Des (1-3) IGF-I resulted in similar curves. Insulin did not displace labeled IGF-I even at very high concentrations (>1 microM), which indicates the specificity of IGF-I binding. The amount of receptor (R(0)) increased from 253 +/- 51 fmol/mg DNA on day 1 to 766 +/- 107 fmol/mg DNA on day 10. However, the affinity (K(d)) of IGF-I receptors did not change significantly during this development (from 1.29 +/- 0.19 to 0.79 +/- 0.13 nM). On the basis of our results, we conclude that rainbow trout muscle cells in culture express specific IGF-I receptors, which increase their number with development from mononuclear cells to large myotubes.
Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, E-08028 Barcelona, Spain.
Juan
J
Castillo
Pierre-Yves
PY
Le Bail
Gilles
G
Paboeuf
Isabel
I
Navarro
Claudine
C
Weil
Benoit
B
Fauconneau
Joaquim
J
Gutiérrez
D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010641:Phenotype; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology
D018969:Insulin-Like Growth Factor Binding Proteins; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1