A specific and highly sensitive time-resolved fluoroimmunoassay for human proinsulin.
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.
Dalbosco
I S
IS
Disciplina de Endocrinologia, Universidade Federal de São Paulo, Brasil.
Vieria
J G
JG
Nishida
S K
SK
Lombardi
M T
MT
Moisés
R C
RC
Coifman
R
R
Russo
E M
EM
D000328:Adult; D000368:Aged; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001665:Binding Sites; D001786:Blood Glucose / Q000032:analysis; D005260:Female; D015200:Fluoroimmunoassay / Q000379:methods*; D018149:Glucose Intolerance / Q000175:diagnosis; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D011384:Proinsulin / Q000096:biosynthesis* / Q000097:blood / Q000276:immunology
D000911:Antibodies, Monoclonal; D001786:Blood Glucose; D007328:Insulin; D011384:Proinsulin