A specific and sensitive radioimmunoassay for rat C-peptide.
A sensitive and specific radioimmunoassay for rat serum C-peptide (RCP) has been developed and validated using a guinea pig anti-rat C-peptide antibody to synthetic rat C-peptide. Negligible crossreactivity (< 0.01%) to human proinsulin was observed, whereas human insulin, human pancreatic polypeptide (hPP), porcine insulin, porcine C-peptide, bovine insulin, rat insulin, porcine-PP, and glucagon, respectively, did not produce measurable displacement of RCP tracer. Human C-peptide even in a supraphysiological concentration range crossreacted poorly (< 0.1%). The sensitivity limit of the assay calculated at +/- 3 standard deviations was 24.2pM (0.07 ng/mL). RCP standard concentrations ranged from 25-1600pM. The intraassay- and between assay-coefficient of variations (CV) were 3.5-6.1% and 4.1-9.5%, respectively. The mean percentage recovery of RCP added to rat serum samples was 100.8 +/- 2%. Serum volume dilution from 25 to 100 microL did not significantly alter the expected RCP level. Migration of rat serum C-peptide and that of synthetic RCP were identical in a Sephadex G-50 chromatographic analysis. The mean fasting and postprandial plasma RCP levels in normal rats were 102 +/- 15 pM and 485 +/- 75pM, respectively. RCP levels following intravenous glucose tolerance test in diabetic and nondiabetic rats were consistent with expected patterns. In conclusion, we have developed and validated a rat C-peptide assay that is sensitive, simple, and specific for RCP in serum. The assay provides a reliable tool for studies of diabetes using rodent animal models.
Akpan
J O
JO
Department of Pediatrics, Washington University, St. Louis, MO 63110.
Weide
L G
LG
Gingerich
R L
RL
D000818:Animals; D002096:C-Peptide / Q000032:analysis* / Q000097:blood; D002845:Chromatography; D004435:Eating; D005215:Fasting; D005951:Glucose Tolerance Test; D007262:Infusions, Intravenous; D008297:Male; D011863:Radioimmunoassay / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D002096:C-Peptide