C-Peptide ELISA
The Calbiotech, Inc. C-peptide ELISA (enzyme-linked immunosorbent assay) kit is intended for the quantitative determination of human C-peptide levels in human serum, plasma, and urine.
Human C-Peptide has a molecular mass of approximately 3000 daltons. C-Peptide has no metabolic function. However, since C-Peptide and insulin are secreted in equimolar amounts, the immunoassay of C-Peptide permits the quantitation of insulin secretion. This is the reason for the clinical interest of serum or plasma determinations of C-Peptide. Moreover, C-Peptide measurement has several advantages over immunoassays of insulin. The half-life of C-Peptide in the circulation is between two and five times longer than that of insulin. Therefore, C-Peptide levels are a more stable indicator of insulin secretion than the more rapidly changing levels of insulin. A very clear practical advantage of C-Peptide measurement arising from its relative metabolic inertness as compared to insulin is that C-Peptide levels in peripheral venous blood are about 5-6 times greater than insulin levels. Also, relative to an insulin assay, the C-Peptide assay’s advantage is its ability to distinguish endogenous from injected insulin. C-Peptide has also been measured as an additional means for evaluating glucose tolerance and glibenclamide glucose tests. C-Peptide levels are in many ways a better measurement of endogenous insulin secretion than peripheral insulin levels. C-Peptide may be measured in either blood or urine. With improved sensitive C-Peptide immunoassays, it is now possible to measure C-Peptide values at extremely low levels. The clinical indications for C-Peptide measurement include diagnosis of insulinoma and differentiation from factitious hypoglycemia, follow-up of pancreatectomy, and evaluation of viability of islet cell transplants. Recently, these indications have been dramatically expanded to permit evaluation of insulin dependence in maturity onset diabetes mellitus.
The C-Peptide is a solid phase direct sandwich ELISA method. The standards, samples and controls are added into the selected wells coated with anti C-Peptide monoclonal anybody. C-Peptide in the standards, controls and patient’s serum binds to anti- C-Peptide Ab on the wells. Unbound protein is washed off by wash buffer. The anti- C-Peptide -HRP conjugated second antibody is added and then binds to C-Peptide. Unbound proteins and HRP conjugate is washed off by wash buffer. Upon the addition of the substrate, the enzyme activities are proportional to the concentration of C-Peptide in the samples. A standard curve is prepared relating color intensity to the concentration of the C-Peptide.
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