title: Most of the circulating insulin-like growth factors-I and -II are present in the 150 kDa complex during human pregnancy.
abstract: The aim of this study was to assess the molecular size distribution of insulin-like growth factors (IGFs) complexed to IGF-binding proteins (IGFBPs) in serum of non-pregnant and pregnant women. Sera were fractionated on a size-exclusion column at pH 7.4 to resolve different IGF-IGFBP complexes from unbound IGFs. Each fraction was further chromatographed on a size-exclusion column under acid conditions to dissociate IGFs from binding proteins prior to measurement of the IGF content of the complexes. The IGF-containing fractions from the acid column were assayed specifically for IGF-I and IGF-II. Serum pooled from pregnant women contained more IGF-I and IGF-II than serum from non-pregnant women. In both groups most of the IGF-I and IGF-II was found in a large (150 kDa) complex in serum and the remainder was present in complexes eluting in the 40-50 kDa region at pH 7.4. Some free IGF-I was also detected. Serum fractions collected by size-exclusion chromatography at pH 7.4 were also analysed by Western-ligand blotting to characterize the IGFBPs in the two main IGFBP size classes. In serum pooled from non-pregnant women, the 150 kDa IGF-IGFBP complexes contained a 40-50 kDa IGFBP doublet following Western-ligand blot analysis. This IGFBP co-migrated with a pure IGFBP-3 standard. IGFBPs of 34, 28 and 24 kDa all contributed to the 40-50 kDa IGF-IGFBP complexes of the pH 7.4 chromatograph.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biochemistry, University of Adelaide, South Australia.
authors.forename: S E
authors.initials: SE
authors.lastname: Gargosky
authors.forename: P C
authors.initials: PC
authors.lastname: Owens
authors.forename: P E
authors.initials: PE
authors.lastname: Walton
authors.forename: J A
authors.initials: JA
authors.lastname: Owens
authors.forename: J S
authors.initials: JS
authors.lastname: Robinson
authors.forename: J C
authors.initials: JC
authors.lastname: Wallace
authors.forename: F J
authors.initials: FJ
authors.lastname: Ballard
mesh_terms: D015153:Blotting, Western; D002352:Carrier Proteins / Q000097:blood*; D005591:Chemical Fractionation; D002845:Chromatography / Q000379:methods; D005260:Female; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008970:Molecular Weight; D011247:Pregnancy / Q000097:blood*
chemical_list: D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II