Heterogeneity of circulating human C-peptide.
Values reported for serum C-peptide immunoreactivity in healthy individuals vary considerably. To assess factors that contribute to this finding, three human C-peptide assay systems were developed utilizing three distinct antisera that react differently with various C-peptide fragments. Preparations of natural pancreatic and synthetic human C-peptide standards were compared immunologically in these systems. The curves of the natural C-peptide and the synthetic preparations were not identical. The relative immunoreactivity of each standard varied, depending on the particular antiserum used. Serum C-peptide concentrations varied when measured in the different assay systems. Furthermore, the results of dilution and recovery tests and stability of the C-peptide during storage showed differences among the three assays. Gel filtration of serum indicated heterogeneity within the major C-peptide peak, and in addition, a smaller peak of lower molecular weight material was present in some samples. Although degradation of serum C-peptide may occur during storage, fragments of C-peptide may also be secreted or arise during in-vivo metabolism. Thus, the present studies indicate the need for careful standardization and checking of each particular assay system before its use in clinical studies.
D002096:C-Peptide / Q000276:immunology; D003429:Cross Reactions; D000939:Epitopes; D006801:Humans; D010179:Pancreas / Q000032:analysis; D010455:Peptides / Q000276:immunology; D011863:Radioimmunoassay
D002096:C-Peptide; D000939:Epitopes; D010455:Peptides