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  • A highly sensitive and specific assay for determination of IGF-I bioactivity in human serum.

A highly sensitive and specific assay for determination of IGF-I bioactivity in human serum.

American journal of physiology. Endocrinology and metabolism (2003-02-27)
Jian-Wen Chen, Thomas Ledet, Hans Orskov, Niels Jessen, Sten Lund, Jonathan Whittaker, Pierre De Meyts, Maj Britt Larsen, Jens Sandahl Christiansen, Jan Frystyk
摘要

At present, the circulating bioactivity of insulin-like growth factor I (IGF-I) is estimated by immunological measurements of IGF-I levels. However, immunoassays ignore the modifying effects of the IGF-binding proteins (IGFBPs) on the interaction between IGF-I and the IGF-I receptor (IGF-IR). Therefore, we developed an IGF-I kinase receptor activation assay (KIRA) based on cells transfected with the human IGF-IR gene. The bioassay was sensitive (detection limit 0.08 microg/l), specific (cross-reactivity of insulin, insulin analogs, and proinsulin was <1%; IGF-II cross-reactivity was 12%), and accurate (within- and between-assay coefficients of variation <7 and <15%). The operational range of the assay (0.25-10.0 microg/l) allowed for determination of IGF-I bioactivity in serum from patients with, for example, growth hormone deficiency, type 1 diabetes, and acromegaly. Addition of IGFBPs dose dependently reduced the KIRA signal, whereas addition of IGF-II to preformed complexes (1:1 molar ratio) of IGF-I and IGFBP dose dependently increased IGF-I bioactivity by displacement of bound IGF-I. In conclusion, the KIRA will enable us to compare IGF-I bioactivity with existing immunological measurements of IGF-I in serum and, hopefully, to elucidate the factors that determine IGF-I bioactivity in vivo.

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Sigma-Aldrich
无水碳酸钠, powder, ≥99.5%, ACS reagent
Sigma-Aldrich
无水碳酸钠, ACS reagent, anhydrous, ≥99.5%, powder or granules
Sigma-Aldrich
无水碳酸钠, ACS reagent (primary standard), anhydrous, 99.95-100.05% dry basis
Sigma-Aldrich
无水碳酸钠, anhydrous, powder or granules, free-flowing, Redi-Dri, ACS reagent, ≥99.5%
Sigma-Aldrich
无水碳酸钠, anhydrous, free-flowing, Redi-Dri, ACS reagent (primary standard), 99.95-100.05% dry basis