ASSAY SYSTEMS FOR THE GROWTH HORMONE-BINDING PROTEIN

The first method used for detection of growth hormone-binding protein (GHBP) in biological fluids was based on the incubation of the sample with radiolabeled GH followed by separation of bound and free GH by ge l exclusion chromatography. Recently, other methods have been develope d which are faster and easier to use. These methods include variants o f the original binding/column assay (e.g., separation of bound and fre e GH is obtained by immunoprecipitation, charcoal adsorption, ion exch ange chromatography, or HPLC), and a ligand-mediated immunofunctional assay (LIFA), in which a monoclonal antibody is used to capture the GH BP on a microtiter plate; all binding sites are saturated with GH and an anti-GH antibody Is used to detect the amount of GH (endogenous and exogenous) hound to the GHBP. To permit comparison of results obtaine d by different methods we have cross-validated the LIFA with two diffe rent binding assays: (i) the original long column assay (column assay) , and (ii) an assay based on immunoprecipitation (RIPA) of the GH/GHBP complex with an anti-GHBP antibody.