Evaluation of a sensitive and specific radioimmunoassay for pancreatic glucagon in human plasma and its clinical application.

A glucagon radioimmunoassay employing antiserum specific for pancreatic glucagon is described. Glucagon was radioiodinated by the chloramine T technique and purified on QAE-Sephadex A 25 to a specific activity of 225 mu Ci/microgram. The standard curve allowed measurements from 12 to 500 pg/ml with sensitivity of 17.5 pg/ml, precision of 6.3-14.9% (CV, within-assay) and 5.6-10.7% (CV, between-assay). Recovery was between 82 and 112%. Fasting plasma glucagon levels in diabetics, obese subjects, acromegalics and patients with Cushing's syndrome were greater than in normals (22.0 +/- 91 pg/ml; mean +/- SD). Very low glucagon levels after oral glucose suppression (15.2 +/- 3.1 pg/ml) in normals and greatly increased values after arginine in insulin-dependent diabetics (271.0 +/- 132.3 pg/ml) could be determined.