title: Characterization of an insulin-like growth factor-I/somatomedin-C radioimmunoassay specific for the C-peptide region.
abstract: Insulin-like growth factor-I (IGF-I) and somatomedin-C )SM-C) have been shown to be functionally identical by a number of criteria. We have synthesized the 12 amino acid C-peptide region of IGF-I (Gly-Tyr-Gly-Ser-Ser-Ser-Arg-Arg-Ala-Pro-Glu-Thr) and developed a RIA based on antibodies against this synthetic peptide. IGF-I and SM-C were indistinguishable in this RIA. No other peptides competed for this antiserum. The SM-C/IGF-I values of acid-chromatographed serum were strongly age dependent. The mean of children 1-5 yr old was 0.67 +/- 0.033 U/ml (mean +/- SD; n = 23), whereas the mean of children 12-17 yr old was 2.01 +/- 0.66 U/ml (n = 39) and the mean of 38 adults 26-85 yr old was 1.05 +/- 0.34. The SM-C/IGF-I values measured by this RIA were also growth hormone dependent. Thus, this region-specific RIA provides a clinically useful assessment of serum SM-C/IGF-I levels.
mesh_terms: D000172:Acromegaly / Q000097:blood; D000328:Adult; D000368:Aged; D000375:Aging; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007018:Hypopituitarism / Q000097:blood; D007223:Infant; D007328:Insulin / Q000097:blood* / Q000276:immunology; D007334:Insulin-Like Growth Factor I; D008875:Middle Aged; D010446:Peptide Fragments / Q000276:immunology*; D011863:Radioimmunoassay / Q000379:methods*; D012016:Reference Values; D013002:Somatomedins / Q000097:blood* / Q000276:immunology
chemical_list: D007328:Insulin; D010446:Peptide Fragments; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I