title: Changes in the hypophysial-gonadal axis during the onset of puberty in young bulls.
abstract: The objectives of this study were to determine the extent of changes in concentrations of testosterone, growth hormone (GH) and insulin-like growth factor I (IGF-I) concentrations in blood plasma and to characterize the respective plasma-binding proteins of these two peptides during the onset of puberty in male calves. The jugular veins of six male Holstein calves (11-weeks-old) were catheterized and blood was collected every 3 days (one sample every 30 min for 8 h). Hormone concentrations in plasma were determined by specific radioimmunoassay. After incubation with [125I]IGF-I, IGF-I-binding proteins (IGFBPs) were separated by gel filtration; radioactivity was determined in each fraction. Western ligand blotting using radiolabelled hormones as ligand was also used to characterize the IGF-I- and GH-binding proteins in plasma. Puberty was characterized by a rapid (in 1 or 2 days) increase in mean concentrations of testosterone in plasma (from 0.5 to > 2 ng ml-1) and a pulsatile release of the hormone. During puberty, IGF-I concentrations also increased rapidly in 8-10 days from +/- 50 ng ml-1 to > 150 ng ml-1, whereas concentrations of GH in plasma remained relatively stable during the experimental period. A significant correlation was observed between IGF-I and testosterone concentrations (r = 0.77; P < 0.001) throughout the experimental period. Three different IGF-I-binding protein fractions with apparent molecular masses of > 200, 150-170 and 45-65 kDa were found in plasma using gel filtration.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Molecular Biology, Faculty of Agronomy, Gembloux, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Renaville
authors.forename: A
authors.initials: A
authors.lastname: Devolder
authors.forename: S
authors.initials: S
authors.lastname: Massart
authors.forename: M
authors.initials: M
authors.lastname: Sneyers
authors.forename: A
authors.initials: A
authors.lastname: Burny
authors.forename: D
authors.initials: D
authors.lastname: Portetelle
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000097:blood; D002417:Cattle / Q000502:physiology*; D002850:Chromatography, Gel; D013006:Growth Hormone / Q000097:blood; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D010902:Pituitary Gland / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology*; D013737:Testis / Q000502:physiology*; D013739:Testosterone / Q000097:blood
chemical_list: D002352:Carrier Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone