Measurement of free insulin-like growth factor-I using immunoradiometric assay.
The free Insulin-like growth factor-I (IGF-I) in plasma from normal adults was directly measured with a newly developed highly sensitive immunoradiometric assay (IRMA) for IGF-I. The capture antibody did not crossreact with IGF-I associated binding proteins which exist in plasma, and the assay was designed not to shift the equilibrium of the IGF-I and binding proteins. Total IGF-I concentration was measured using this assay with preliminary acid-ethanol extraction. Approximately 1 percent of total IGF-I existed in the free form. Gel filtration of plasma was also used to separate the free IGF-I from its bound form. The free/total ratio of IGF-I as determined by gel filtration was similar to that determined directly by IRMA with and without acid-ethanol extraction.
Takada
M
M
Mitsubishi Petrochemical Co., Ltd., Ibaraki, Japan.
Nakanome
H
H
Kishida
M
M
Hirose
S
S
Hasegawa
T
T
Hasegawa
Y
Y
D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D015153:Blotting, Western; D002352:Carrier Proteins / Q000276:immunology; D002850:Chromatography, Gel; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods*; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000737:chemistry
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I