Estimation of Somatomedin-C Levels in Normals and Patients with Pituitary Disease by Radioimmunoassay

作者：Richard W. Furlanetto, Louis E. Underwood, Judson J. Van Wyk, A. Joseph D’Ercole · 发表于：Journal of Clinical Investigation · 年份：1977 · DOI：10.1172/jci108816 · 被引用次数：855 · 研究领域：Monoclonal and Polyclonal Antibodies Research、Myasthenia Gravis and Thymoma、Cell Adhesion Molecules Research

The development of a radioimmunoassay for somatomedin-C has for the first time made it possible to discriminate between serum concentrations of a single peptide or closely related group of peptides and the net somatomedin activity measured by less specific bioassay and radioreceptor techniques. Antibodies to human somatomedin-C were raised in rabbits using a somatomedin-C ovalbumin complex as the antigen. A variety of peptide hormones at concentrations up to 1 muM are not recognized by the antibody. Insulin at concentrations >0.1 muM cross reacts in a non-parallel fashion; purified somatomedin-A is only 3% as active as somatomedin-C; and radiolabeled cloned rat liver multiplication stimulating activity does not bind to the antibody. Immunoreactive somatomedin-C can also be quantitated in the sera of a variety of subhuman species. Unusual assay kinetics, which are manifest when reactants are incubated under classic "equilibrium" assay conditions, appear to result from the failure of (125)I-somatomedin-C to readily equilibrate with the somatomedin-C serum binding protein complex. It is, therefore, necessary to use nonequilibrium assay conditions to quantitate somatomedin-C in serum. With this assay it is possible to detect somatomedin-C in normal subjects using as little as 0.25 mul of unextracted serum. Serum somatomedin-C concentrations in normal subjects were lowest in cord blood and rose rapidly during the first 4 yr of life to near adult levels. In 23 normal adult voluntee...