Assessment of developmental changes in chicken and turkey insulin-like growth factor-II by homologous radioimmunoassay.
The development of a homologous RIA for chicken insulin-like growth factor-II (cIGF-II) and its application to investigate the developmental changes in IGF-II in the chicken and turkey are described. A double-antibody RIA has been developed using recombinantly derived cIGF-II as antigen, radiolabelled tracer and standard. Serial dilutions of chicken and turkey plasma were parallel to serial dilutions of cIGF-II standard. We have also established that acid/ethanol extraction of chicken and turkey plasma reduced possible interference of insulin-like growth factor-binding proteins in the RIA. Consumption of a low-protein diet by male chickens lowered plasma IGF-I twofold, whereas IGF-II levels were unchanged. Food withdrawal evoked an increase in circulating IGF-II, while IGF-I levels were reduced. Refeeding returned both growth factors to normal circulating concentrations. During chick embryo incubation, plasma IGF-II levels were tenfold higher than those of IGF-I. In the turkey embryo, plasma IGF-II concentrations were higher than those of IGF-I. During the post-hatch period. IGF-II levels declined with age in chickens. In the growing turkey, IGF-II levels were consistently higher than IGF-I levels. The application of the homologous RIA to monitor plasma levels during embryonic development and post-hatch growth in avian species will provide more accurate comparisons of results from studies on the role of IGF-II in growth and metabolism of domestic birds.
United States Department of Agriculture, Growth Biology Laboratory, Beltsville, Maryland 20705, USA.
J P
JP
McMurtry
R W
RW
Rosebrough
D M
DM
Brocht
G L
GL
Francis
Z
Z
Upton
P
P
Phelps
D000818:Animals; D002642:Chick Embryo; D002645:Chickens / Q000097:blood / Q000254:growth & development*; D004044:Dietary Proteins / Q000008:administration & dosage; D006168:Guinea Pigs; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000032:analysis* / Q000378:metabolism; D011863:Radioimmunoassay; D014422:Turkeys / Q000097:blood / Q000196:embryology / Q000254:growth & development*
D004044:Dietary Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II