title: Heterogeneity of circulating C-peptide.
abstract: Serum C-peptide levels vary when measured with different immunoassay systems. In order to assess the factors contributing to this finding, serum C-peptide was measured in two assays utilizing different antisera, but the same standards and labeled peptide. The antisera were characterized with synthetic C-peptide fragments and their reactivities towards some of these fragments differed. The results of dilution and recovery tests and stability of the C-peptide during storage showed differences between the two assays. Gel filtration experiments indicated heterogeneity within the major C-peptide peak, and, in addition, a smaller peak of lower molecular weight material was present in some sera. Although degradation of serum C-peptide may occur during storage or with freezing and thawing, fragments of C-peptide may also be secreted or arise during in vivo metabolism.
mesh_terms: D000818:Animals; D002096:C-Peptide / Q000097:blood* / Q000276:immunology; D002850:Chromatography, Gel; D004355:Drug Stability; D006168:Guinea Pigs / Q000276:immunology; D006801:Humans; D007700:Kinetics; D010455:Peptides / Q000097:blood*; D011863:Radioimmunoassay
chemical_list: D002096:C-Peptide; D010455:Peptides