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Measurement of an analog of insulin-like growth factor-I in blood plasma using a novel enzyme-linked immunosorbent assay

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dc.contributor.authorGajanandana, O.
dc.contributor.authorIrvine, K.
dc.contributor.authorGrant, P.
dc.contributor.authorFrancis, G.
dc.contributor.authorKnowles, S.
dc.contributor.authorWrin, J.
dc.contributor.authorWallace, J.
dc.contributor.authorOwens, P.
dc.date.issued1998
dc.description.abstractLong-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.
dc.description.statementofresponsibilityO Gajanandana, K Irvine, PA Grant, GL Francis, SE Knowles, J Wrin, JC Wallace, and PC Owens
dc.identifier.citationJournal of Endocrinology, 1998; 156(3):407-414
dc.identifier.doi10.1677/joe.0.1560407
dc.identifier.issn0022-0795
dc.identifier.issn1479-6805
dc.identifier.orcidWrin, J. [0000-0003-3584-7343]
dc.identifier.urihttp://hdl.handle.net/2440/8284
dc.language.isoen
dc.publisherJ ENDOCRINOLOGY LTD
dc.rightsCopyright © 1998 Journal of Endocrinology Ltd
dc.source.urihttps://doi.org/10.1677/joe.0.1560407
dc.subjectAnimals
dc.subjectMice, Inbred BALB C
dc.subjectCattle
dc.subjectRabbits
dc.subjectMice
dc.subjectHormones
dc.subjectInsulin-Like Growth Factor I
dc.subjectInsulin-Like Growth Factor Binding Proteins
dc.subjectRadioimmunoassay
dc.subjectEnzyme-Linked Immunosorbent Assay
dc.subjectSensitivity and Specificity
dc.titleMeasurement of an analog of insulin-like growth factor-I in blood plasma using a novel enzyme-linked immunosorbent assay
dc.typeJournal article
pubs.publication-statusPublished

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