Specific immunoradiometric assay of insulin-like growth factor I with use of monoclonal antibodies.
We identified two monoclonal antibodies that bind spatially distinct epitopes on insulin-like growth factor I (IGF-I). Using these two antibodies, we developed a simultaneous, two-site immunoradiometric assay (IRMA) specific for IGF-I. This IRMA has no detectable cross reactivity with insulin, proinsulin, prolactin, or somatotropin, and less than 2% crossreactivity with IGF-II. The assay response varies linearly with IGF-I concentrations of 0-800 micrograms/L in serum; the detection limit is about 10 micrograms/L. A comparison of 26 IGF-I serum values from the IRMA and from a previously reported IGF-I specific RIA gave a correlation coefficient of 0.96 with no substantial bias (slope = 1.10). IGF-I values for serum, as an aid in assessing growth abnormalities, are easily (only three pipetting steps) obtained in less than 4 h.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007118:Immunoassay; D007334:Insulin-Like Growth Factor I / Q000097:blood* / Q000276:immunology; D007457:Iodine Radioisotopes; D051379:Mice; D008807:Mice, Inbred BALB C; D011786:Quality Control; D011863:Radioimmunoassay; D012044:Regression Analysis; D013002:Somatomedins / Q000097:blood*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D007457:Iodine Radioisotopes; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I