A SPECIFIC AND HIGHLY SENSITIVE TIME-RESOLVED FLUOROIMMUNOASSAY FOR HUMAN PROINSULIN

We describe a time-resolved fluoroimmunoaaaay specific for human Key w ords proinsulin using a combination of two high-affinity monoclonal an tibodies, one against insulin and the other specific for intact proins ulin and for split 65-66 and des 64-65 proinsulin forms. The assay emp loys only 200 mu l 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 an alyzed in 50 subjects during an oral glucose tolerance test (10 non-ob ese controls, 10 obese controls, 10 subjects with impaired glucose tol erance, 10 patients with type II diabetes mellitus (DM) and fasting bl ood 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 ass ay in non-obese controls (0.84 +/- 0.90 pmol/l; 0.1-2.4 pmol/l) were l ower than the results reported by other investigators. There was an in crease of proinsulin related to obesity and increased glucose levels, suggesting that proinsulin levels increase with insulin resistance.