Measurement of free insulin—like growth factor—i using immunoradiometric assay

Makoto Takada, Hiroyuki Nakanome, Mariko Kishida, Sachio Hirose, Tomonobu Hasegawa, Yukihiro Hasegawa

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50 Citations (Scopus)


The free Insulin-like growth factor-I (IGF-I) in plasma from normal adults was directly measured with a newly developed highly sensitive immunoradiometric assay (IRMA) for IGF-I. The capture antibody did not crossreact with IGF-I associated binding proteins which exist in plasma, and the assay was designed not to shift the equilibrium of the IGF-I and binding proteins. Total IGF-I concentration was measured using this assay with preliminary acid—ethanol extraction. Approximately 1 percent of total IGF-I existed in the free form. Gel filtration of plasma was also used to separate the free IGF-I from its bound form. The free/total ratio of IGF-I as determined by gel filtration was similar to that determined directly by IRMA with and without acid—ethanol extraction.

Original languageEnglish
Pages (from-to)263-276
Number of pages14
JournalJournal of Immunoassay
Issue number3
Publication statusPublished - 1994 Aug 1
Externally publishedYes


  • form binding protein
  • immunoradiometric assay Western immunoblot)
  • insulin
  • like growth factor-I free

ASJC Scopus subject areas

  • Immunology
  • Pharmacology


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