By hydrophobic gel permeation and high pressure liquid chromatography we isolated from pig intestinal mucosa a peptide which corresponds to proglucagon 78–107 as suggested by chromatography and determination of its N-terminal sequence. Natural and synthetic proglucagon 78–107 dose dependently and potently increased insulin secretion from the isolated perfused pig pancreas. Proglucagon 78–107 also secreted by the small intestine may participate in the hormonal control of insulin secretion.
