Radioimmunoassay for insulin-like growth factor-I: solutions to some potential problems and pitfalls

• DOI: 10.1677/joe.0.1280347
• Publication Date: 2008-12-11T23:11:20Z
• Authors: B. H. Breier; B. W. Gallaher; P. D. Gluckman
• Keywords: Sephadex; Somatomedin; Blood plasma; Radioligand

This report describes essential requirements for the validation of a radioimmunoassay (RIA) insulin-like growth factor-I (IGF-I) and presents solutions to some problems pitfalls commonly observed. The preparation IGF-I be used as radioligand or standard has selected carefully since preparations are contaminated with variants which demonstrate different potencies antisera in RIA. Accurate assessment levels blood plasma requires an efficient extraction method IGF-binding proteins (IGFBPs). Extraction methods remove influence IGFBPs RIA were compared using considerable differences IGF-I/IGFBP ratios. Acidification before column chromatography on Sephadex G-75 (G75) is generally considered most reliable method, but it very time-consuming. acid-ethanol (AE) not valid many situations. Non-parallel displacement was observed AE-extracted samples In addition, comparison values obtained after AE G75 fetal ovine shown no significant correlation. We technique based modified followed by cryo-precipitation (AEC). AEC reduced residual level that did interfere assay. Furthermore, AEC-extracted showed parallel highly purified authentic IGF-I. high correlations, slope close unity, from species including adult sheep, rat, mouse man. provides rapid simple alternative variety provided high-affinity