A radioreceptor-assay for glucagon: binding of enteroglucagon to liver plasma membranes

A radioreceptor-assay for glucagon was developed employing pig liver plasma membranes isolated by means of an aqueous two-phase polymer system. The assay is simple, precise, and has a detection limit of 40 pg/ml. Acid-ethanol extracts of porcine intestinal mucosa and entero-glucagon purified by affinity chromatography interfered strongly with the binding of 125I-labelled glucagon. The affinity of enteroglucagon for the membranes was lower than that of glucagon, but even physiological concentrations of the former interfere with glucagon binding, indicating that enteroglucagon may compete with pancreatic glucagon for binding to the hepatocyte under physiological conditions.