Developmental changes in chicken and turkey insulin-like growth factor-I (IGF-I) studied with a homologous radioimmunoassay for chicken IGF-I.
The development of a homologous radioimmunoassay (RIA) for chicken insulin-like growth factor-I (cIGF-I) and its use to investigate the developmental changes in IGF-I in the chicken and turkey is described. A double-antibody RIA has been developed using recombinantly derived cIGF-I as antigen, radiolabelled tracer and standard. The resulting immunoassay has a minimum detection limit of 0.035 ng and effective dose of 2.5 ng. Dose-response curves of chicken and turkey plasma and tissue extracts were parallel with cIGF-I standard. The antiserum is specific for IGF-I as no cross-reactivity with chicken IGF-II, insulin, glucagon, gastrin or avian pancreatic polypeptide was observed. We have also established that acid/ethanol extraction of chicken and turkey plasma reduced possible interference of IGF-binding proteins (IGFBPs) in the RIA. Comparison of IGF-I immunoactivity in unextracted and acid/ethanol-extracted samples following gel filtration under acidic and neutral conditions indicates that the cIGFBPs may be acid-labile. Analyses of samples from growing chickens and turkeys using the homologous avian reagents revealed higher IGF-I concentrations than if the IGF were quantified using heterologous mammalian-derived reagents. A similar pattern was observed when tissue extracts were assayed for IGF-I content. The application of the homologous RIA to monitor blood and tissue IGF-I levels during embryonic development and posthatch growth in avian species will provide more accurate comparisons of results from studies on the role of IGF-I in growth and metabolism of domestic birds.
McMurtry
J P
JP
United States Department of Agriculture, Nonruminant Animal Nutrition Laboratory, Beltsville, Maryland 20705.
Francis
G L
GL
Upton
F Z
FZ
Rosselot
G
G
Brocht
D M
DM
D000818:Animals; D002645:Chickens / Q000097:blood / Q000254:growth & development / Q000378:metabolism*; D002850:Chromatography, Gel; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000378:metabolism; D011863:Radioimmunoassay / Q000379:methods*; D012680:Sensitivity and Specificity; D014422:Turkeys / Q000097:blood / Q000254:growth & development / Q000378:metabolism*
D007334:Insulin-Like Growth Factor I