A homologous radioimmunoassay for rat insulin-like growth factor-I (IGF-I): Implications for studies of human IGF-I physiology

Phillip Lee, Bonita K. Baker, Frances Liu, Elaine Y W Kwan, Raymond L. Hintz

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21 Scopus citations


We report the development of a unique radioimmunoassay (RIA) for rat insulin-like growth factor-I (rIGF-I) which does not recognize human IGF-I (hIGF-I). The rIGF RIA uses a specific anti-rIGF-I antiserum with rIGF-I standards and radioligand. Rat sera were extracted by either an abbreviated acid/ethanol procedure or by acid-chromatography with virtually identical results. Assay sensitivity is 0.5 ng/tube and inter- and intra- assay coefficients of variation were 3.4-7.6% and 4.8-9.2%, respectively. Comparisons of the rIGF-I RIA with a typical heterologous RIA shows that the latter underestimates rIGF-I levels by 3-fold. Sera from rats treated with hIGF-I were also studied using the rIGF-I RIA and a hIGF-I-specific immunoradiometric assay (IRMA), and results indicate poor correlation between the actual total IGF-I levels (rIGF-I RIA + hIGF-IRMA) and the heterologous RIA estimates. The availability of both rIGF-I and hIGF-I specific immunoassays facilitates more precise studies of hIGF-I in the rat model.

Original languageEnglish (US)
Pages (from-to)2002-2005
Number of pages4
JournalJournal of Clinical Endocrinology and Metabolism
Issue number5
StatePublished - 1996
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

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