title: Insulin-like growth factor binding protein-3 is present in the alpha-granules of platelets.
abstract: The lysis of the alpha-granules of platelets has been shown to release insulin-like growth factors (IGFs). One of the major regulators of the activity of IGFs is the IGF binding proteins (IGFBPs), but IGFBPs were thought to be absent from platelet alpha-granules. Human platelets were isolated, and the contents of the alpha-granules were released by thrombin digestion. IGFBP-3 was identified in the lysate by RIA and a ligand-binding Western blot; no other IGFBPs were observed. Platelet IGFBP-3 was present as the characteristic glycosylated doublet at 45 and 43 kilodaltons on ligand-binding Western blot, but was not associated with the acid-labile subunit in the alpha-granule. Thus, the IGFs in platelet alpha-granules coexist with IGFBP-3, which can play a major role in regulating and targeting the actions of IGFs when released by lysis.
authors.affiliation: Laboratory of Growth and Development, California Pacific Medical Center, San Francisco 94118.
authors.forename: E M
authors.initials: EM
authors.lastname: Spencer
authors.forename: A
authors.initials: A
authors.lastname: Tokunaga
authors.forename: T K
authors.initials: TK
authors.lastname: Hunt
mesh_terms: D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000097:blood* / Q000302:isolation & purification; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D003594:Cytoplasmic Granules / Q000378:metabolism*; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000378:metabolism*; D008970:Molecular Weight; D011863:Radioimmunoassay; D013917:Thrombin / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013917:Thrombin