Interference of immunoglobulins in two glucagon radioimmunoassays

• Radioimmunoassays of glucagon in plasma may be complicated by interaction with other substances of high molecular mass. Precipitates of such substances with ammonium sulfate showed, after isoelectric focusing, two fractions having glucagon immunoreactivity. One fraction (pl approximately 10) evidently is associated with the Fc portion (but not the Fab portion) of purified polyclonal immunoglobulin G (IgG). Equal amounts of purified monoclonal IgG of various subclasses, especially IgG 1, gave different "glucagon" readings, suggesting that some IgG may interfere more strongly than others. The other fraction (pI 5-6) appeared less consistently, and on gel chromatography appeared to be slightly larger than IgG. Together these fractions add about 50-100 ng/L to the immunoreactive glucagon values in plasma. Therefore methods in which glucagon is extracted before assay should be used for determining the concentration of glucagon present physiologically.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Läkemedelskemi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Medicinal Chemistry (hsv//eng)

Keyword

Ammonium Sulfate

Chromatography, Gel

Cross Reactions

False Positive Reactions

Glucagon/blood

Humans

Immunoglobulin G

Isoelectric Focusing

Molecular Weight

Radioimmunoassay

Publication and Content Type

art (subject category)

ref (subject category)