Different forms of insulin-like growth factor-binding protein-3 detected in serum and seminal plasma by immunofluorometric assay with monoclonal antibodies
Koistinen, H.; Seppälä, M.; Koistinen, R.
Clinical Chemistry 40(4): 531-536
1994
ISSN/ISBN: 0009-9147 PMID: 7511996 Document Number: 434653
Monoclonal antibodies against recombinant insulin-like growth factor-binding protein-3 (IGFBP-3) were produced to study the various forms of IGFBP-3 and to develop a specific immunofluorometric assay. We tested seven antibodies that showed no cross-reactions with the other five human IGFBPs. By immunoblotting, the main bands in normal serum were seen at gt 90, 45, 41, 29, and 25 kDa. In pregnancy serum, the 29-kDa band was stronger, and the double band at 41-45 kDa was weaker or totally absent. We characterized two immunofluorometric assays. IGF-I had no effect on either assay. Added IGF-11 lowered the amount of recombinant IGFBP-3 measured by the 5C11/7F8 assay, but not by the 1 B6/5Cl 1 assay. In normal serum and follicular fluid, IGFBP-3 measurements were lower by the 5C11/7F8 assay, but in most pregnancy sera and amniotic fluids the assays gave similar results. The 5011/7F8 assay also detected IGFBP-3 in seminal plasma, whereas the 1 B6/5C11 assay did not. We conclude that the results of IGFBP-3 measurement depend on the antibodies used, and that different antibodies are suitable for the IGFBP-3 measurement in different body fluids.