The use of perfused rat intestine to characterise the glucagon-like immunoreactivity released into serosal secretions following stimulation by glucose

Isolated perfused intestine of rat was used to demonstrate the glucose-stimulated release of glucagon-like immunoreactivity (GLI) into serosal secretions. The released GLI was characterised using immunoaffinity chromatography on columns of immobilised antibodies specific for the N (residues 1 to 18) and for the C (residues 19-29) terminal portions of glucagon followed by gel-filtration. The immunoreactivity was present in a variety of molecular species. These include a large GLI which has a molecular weight about 12000 and binds to antibodies specific for the N-terminal portion of glucagon and two polypeptide fractions with molecular weight closer to that of glucagon. While one fraction of the small GLI bound both to antibodies specific for the C-terminal and N-terminal portions of glucagon the other bound only to the former antibodies. The relevance of these findings to the origins of circulating GLI and the possible precursor relationships between large and other forms of GLI is discussed.