title: Human C-peptide. Part I: Radioimmunoassay.
abstract: Synthetic human C-peptide bearing a Tyrosine group at its amino end is labelled with 125iodine using chloramin T or hydrogen peroxide and lactoperoxidase. The results are compared applying both methods. Antiserum to synthetic human C-peptide (without Tyrosine) which was partially compared to rabbit albumin, is raised in guinea pigs and goats. Goats show to be superior to guinea pigs concerning antibody production. The so-called "hook effect" phenomenon is observed in setting up the standard curves for the radioimmunoassay. Monotonically decreasing standard curves are obtained on dilution of antiserum with a high antibody titer which was produced by repeated immunization in goats. Free C-peptide and C-peptide bound to antiserum are separated with the anxion exchange resin Amberlite. Using this separation technique we excluded unspecific binding of labelled C-peptide to protein fractions in serum of diabetics. The sensitivity of our radioimmunoassay is approx. 0.3 ng C-peptide/ml serum. Intra- and interassay variability are below 10%. Human proinsulin is the only substance found to crossreact with the antiserum.
mesh_terms: D000818:Animals; D002096:C-Peptide / Q000032:analysis*; D003429:Cross Reactions; D006041:Goats / Q000276:immunology; D006168:Guinea Pigs / Q000276:immunology; D006801:Humans; D007106:Immune Sera; D007456:Iodine Isotopes; D007553:Isotope Labeling / Q000379:methods; D010187:Pancreatic Hormones / Q000032:analysis*; D010455:Peptides / Q000032:analysis*; D011863:Radioimmunoassay / Q000379:methods
chemical_list: D002096:C-Peptide; D007106:Immune Sera; D007456:Iodine Isotopes; D010187:Pancreatic Hormones; D010455:Peptides