Takada M, Nakanome H, Kishida M, Hirose S, Hasegawa T, Hasegawa Y
Mitsubishi Petrochemical Co., Ltd., Ibaraki, Japan.
J Immunoassay. 1994 Aug;15(3):263-76. doi: 10.1080/15321819408009577.
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.
