Enzyme Immunoassay for Determination of Pancreatic Glucagon in Plasma

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Abstract
An enzyme immunoassay (EIA) for determining glucagon levels in plasma specimens [human, rat] was established by using .beta.-D-galactosidase as label. The enzyme conjugate used in the assay could be stored at 4.degree. C for 5 mo. with only a slight decrease in enzymatic and immunological activities. Antiserum [raised in rabbits] N6E raised against the C-terminal peptide (15-29) [porcine] was used at a final dilution of 1:200,000 with the C-terminal peptide (21-29)-enzyme conjugate in the EIA, and compared with antiserum 30K in the conventional radioimmunoassay (RIA). Plasma immunoreactive glucagon (IRG) levels determined by this EIA correlated well with those obtained by the 30K-RIA (r = 0.974), while the absolute values of the IRG levels were slightly different. A similar difference in plasma IRG levels was also found between N6E- and 30K-EIA. The difference might be explained by the results that the N6E-immunoreactivity was less against big plasma glucagon in plasma than the 30K-immunoreactivity.