A specific and highly sensitive time-resolved fluoroimmunoassay for human proinsulin

• Published in: Brazilian journal of medical and biological research Vol. 29; no. 2; p. 193
• Main Authors: Dalbosco, I S, Vieria, J G, Nishida, S K, Lombardi, M T, Moisés, R C, Coifman, R, Russo, E M
• Format: Journal Article
• Language: English
• Published: Brazil 01.02.1996
• Subjects: Adult; Aged; Animals; Antibodies, Monoclonal - pharmacology; Binding Sites; Blood Glucose - analysis; Female; Fluoroimmunoassay - methods; Glucose Intolerance - diagnosis; Humans; Insulin - metabolism; Male; Mice; Mice, Inbred BALB C; Middle Aged; Proinsulin - biosynthesis; Proinsulin - blood; Proinsulin - immunology
• ISSN: 0100-879X

We describe a time-resolved fluoroimmunoassay specific for human proinsulin using a combination of two high-affinity monoclonal antibodies, one against insulin and the other specific for intact proinsulin and for split 65-66 and des 64-65 proinsulin forms. The assay employs only 200 microl of serum, with a detection limit of 0.1 pmol/l. The intra-assay variation coefficient was less than 3% between 3 and 1000 pmol/l. There was 0% cross-reaction with insulin, C-peptide, split 32-33 and des 31-32 proinsulin. Serum concentration of proinsulin was analyzed in 50 subjects during an oral glucose tolerance test (10 non-obese control, 10 obese controls, 10 subjects with impaired glucose tolerance, 10 patients with type II diabetes mellitus (DM) and fasting blood glucose (FBG) < 140 mg/dl, and 10 patients with type II DM and FBG > 150 mg/dl). Mean fasting serum proinsulin levels measured by this assay in non-obese controls (0.84 - 0.90 pmol/l; 0.1-2.4 pmol/l) were lower than the results reported by other investigators. There was an increase of proinsulin related to obesity and increased glucose levels, suggesting that proinsulin levels increase with insulin resistance.