Production and characterization of an antiserum against pancreatic glucagon.

To produce a carboxy-terminal specific antiserum against pancreatic glucagon, glucagon was coupled mainly via its amino-terminal histidine to thyroglobulin, using the amino group reactive pentandial at pH 7.0 for the conjugation procedure. After repeated immunization of rabbits, one high titer antiserum was obtained with a combining site recognizing a part of the carboxy-terminal portion of glucagon as judged from the cross-reaction curves with glucagon fragments, duck pancreatic glucagon and gut glucagon-like immunoreactive substances. There was no cross-reaction with secretin, vasoactive intestinal peptide, and gastric inhibitory peptide. In spite of strong immunoreactive similarities with the antiserum 30K (Unger) this antiserum results in determinations of a somewhat higher amount of plasma immunoreactive glucagon (IRG). The difference was found to depend on a higher content of IRG with a molecular size close to immunoglobulin IgG. A patient with agamma-globulinemia had no measurable IRG of molecular size close to that of IgG, indicating a possible competitive binding of some immunoglobulins to the antiserum.