A homologous radioimmunoassay for quantification of insulin-like growth factor-binding protein-2 in blood from cattle.
Insulin-like growth factor-I and -II (IGF-I, IGF-II) circulate in biological fluids bound to six different IGF-binding proteins that regulate IGF bioactivity. The IGF-binding protein-2 is regulated by growth hormones, and its concentration depends on nutrition and physiological state. Specific antibodies directed against bovine IGF-binding protein-2 were produced, and IGF-binding protein-2 levels in bovine blood samples were quantified by radioimmunoassay. Parallel displacement curves showed strong cross-reactivity with bovine and ovine plasma, were low with porcine plasma, and no cross-reactivity with rat or chicken plasma. Addition of IGF-I or -II to a control pool of bovine plasma did not significantly alter control IGF-binding protein-2 values in a radioimmunoassay. Six nycthemeral periods, determined for three young bulls bled on two occasions, showed that IGF-binding protein-2 plasma levels were stable throughout the day; two or three samples were sufficient to characterize the animal. Cows treated with recombinant bovine somatotropin (bST) had significantly lower serum levels of IGF-binding protein-2 than did control cows. Furthermore, IGF-binding protein-2 levels were dramatically increased at the onset of lactation. This radioimmunoassay for bovine IGF-binding protein-2, which enables quantitative assessment of IGF-binding protein-2 concentration in cattle, confirmed that IGF-binding protein-2 concentrations are depressed by administration of bST, enhanced after calving, and showed absence of diurnal variation.
Vleurick
L
L
Department of Animal Physiology and Molecular Biology, Gembloux Agricultural University, Belgium.
Renaville
R
R
VandeHaar
M
M
Hornick
J L
JL
Istasse
L
L
Parmentier
I
I
Bertozzi
C
C
Van Eenaeme
C
C
Portetelle
D
D
D000818:Animals; D015153:Blotting, Western; D002417:Cattle / Q000097:blood*; D002940:Circadian Rhythm; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood*; D011247:Pregnancy; D011863:Radioimmunoassay / Q000379:methods*; D012016:Reference Values; D012680:Sensitivity and Specificity; D012756:Sheep / Q000097:blood; D013552:Swine / Q000097:blood
D018971:Insulin-Like Growth Factor Binding Protein 2; D013006:Growth Hormone