Identification and characteristics of a 37 000 M(r) insulin-like growth factor binding protein in canine serum

M. E. White, M. R. Hathaway, A. J. Lepine, W. R. Dayton

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Insulin-like growth factors (IGFs) are potent stimulators of cellular growth and their half-life and biological activity are regulated by specific IGF binding proteins (IGFBPs). Western ligand blots of non-reduced human, bovine, ovine and porcine sera reveal an IGFBP-2 band at approximately 34 000 M(r). However, canine sera appear to contain a unique 37 000 M(r) IGFBP and lack the 34 000 M(r) IGFBP-2 band. In order to identify and characterize the 37 000 M(r) IGFBP, adult canine serum was subjected to non-reducing SDS polyacrylamide gel electrophoresis (PAGE), transferred to nitrocellulose paper, followed by [125I]-IGF-1 ligand blotting or immunoblotting with commercially available IGFBP antibodies. The 37 000 M(r) canine IGFBP reacted with an anti-IGFBP-2 antibody indicating that it is a canine analogue of IGFBP-2. However, the large difference in apparent molecular size indicates that this is a unique molecular form of IGFBP-2. N- or O-glycanase treatment of canine sera did not alter the molecular size of canine IGFBP-2 indicating that it is not a glycosylated variant of the IGFBP. Subjecting canine sera to reducing SDS-PAGE followed by anti-IGFBP-2 western immunoblotting revealed that the actual molecular weight of the canine IGFBP-2 is similar to that of reduced IGFBP-2 from other species indicating similar peptide lengths. Thus, the increased non-reduced size of the canine 37 000 M(r) IGFBP-2 is possibly due to a unique secondary structure. Copyright (C) 1998 Elsevier Science Inc.

Original languageEnglish (US)
Pages (from-to)325-330
Number of pages6
JournalComparative Biochemistry and Physiology - B Biochemistry and Molecular Biology
Issue number2
StatePublished - 1998


  • Canine
  • IGFBP-2
  • Immunoblot
  • Insulin-like growth factor binding protein-2
  • Ligand blot
  • Molecular size
  • Molecular weight


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