Measurement of an analog of insulin-like growth factor-I in blood plasma using a novel enzyme-linked immunosorbent assay
Date
1998
Authors
Gajanandana, O.
Irvine, K.
Grant, P.
Francis, G.
Knowles, S.
Wrin, J.
Wallace, J.
Owens, P.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Journal of Endocrinology, 1998; 156(3):407-414
Statement of Responsibility
O Gajanandana, K Irvine, PA Grant, GL Francis, SE Knowles, J Wrin, JC Wallace, and PC Owens
Conference Name
Abstract
Long-Arg³-IGF-I (LR³IGF-I) is a synthetic analog of IGF-I that has much lower affinity for IGF-binding proteins than do native IGFs-I and -II. Comparisons of the effects of LR³IGF-I with those of IGFs-I and -II in in vitro and in vivo studies have proved useful in defining the functions of IGF-binding proteins. We have developed a sensitive noncompetitive nonisotopic assay of LR³IGF-I. Mouse IgG 1A7–F5–E5 binds an epitope that contains the substituted arginine³ in LR³IGF-I and was used as the solid phase antibody. The solution phase antibody was a rabbit immunoglobulin Nelson which binds to an epitope that is common to IGF-I and LR³IGF-I. The ELISA system was able to detect as little as 50 pg LR³IGF-I in 100 μl and the native peptides IGFs-I and -II have less than 0•01% activity. Blood plasma from animals treated with pharmacologically active doses of this growth factor analog could be diluted 33•3-fold before assay, at which concentrations plasma had no significant effect on the assay. The ELISA response to LR³IGF-I was unaffected by the presence of IGF-binding proteins. The intra-assay and interassay coefficients of variation are 2•8 and 7•3% respectively. Recovery of LR³IGF-I added to blood plasma was 90%. The ELISA was used to measure LR³IGF-I concentrations in plasma of cows treated with a pharmacologically active dose of this peptide and the results were compared with those obtained by a previously established LR3IGF-I RIA that requires size exclusion chromatography of plasma under acidic conditions to eliminate IGF-binding protein artefacts from the RIA. There was a positive correlation between results obtained by the two assays. The LR³IGF-I ELISA permits discrimination between the exogenous synthetic IGF-I analog and the endogenous native IGFs-I and -II in animals treated with this growth factor without the need for radioiodination of LR³IGF-I and elimination of the requirement for extraction of plasma before assay.
School/Discipline
Dissertation Note
Provenance
Description
Access Status
Rights
Copyright © 1998 Journal of Endocrinology Ltd