[Human proinsulin-C-peptide radioimmunoassay method; stability of the assay kit].

We have been studies time sequent stability each on standard human-C-peptide, human-C-peptide antiserum, 125I-tyrosyl human-C-peptide and the assay kit (all reagent) which is necessary in human proinsulin-C-peptide radioimmunoassay(RIA). Also we measured using this assay system, human proinsulin C-peptide in blood after oral administration of glucose to normal subject. Standard human-C-peptide and human-C-peptide antiserum were very stable on storage at 4 degrees C, 125I-tyrosyl human-C-peptide was unstable as compared with the former two, The stability of the assay kit was influenced by the stability of 125I-tyrosyl human-C-peptide, and was stable at 4 degrees C for ten weeks after preparation. Three lots of the assay kit prepared at different period showed almost same stability. We think this assay system using the assay kit is satisfactory in respect of stability. The measured values of human proinsulin-C-peptide in blood, using this assay system, showed insulin secretory reaction after oral administration of glucose.