Salivary gland glucagon in man and animals

Abstract

E XTRAPANCREATIC GASTROINTESTINAL SOURCES of immunoreactive glucagon-like substances have been recognized almost since the advent of the immun0assay for glucagon? In an effort to discriminate between these various glucagons, antisera which crossreact poorly with acid-alcohol extracts of gastrointestinal mucosa have been used to measure glucagon believed to be pancreatic in origin. With the discovery that immunoreactive glucagon (IRG) levels, measured with one of these highly specific antisera (Unger 30K), rise following total pancreatectomy, 2-4 it seemed that IRGs similar, if not identical to pancreatic glucagon, might also arise from extrapancreatic gastrointestinal sources, and such a material has now been described from the gastric fundus of dogs. 5 Subsequently, however, Penhos et al. described the presence of, and continued rise in circulating glucagon levels, measured with 30K, in rats subjected to both pancreatectomy and total eviscerectomy. 6 To search for other unrecognized extrapancreatic sources of IRG, we examined extracts of several tissues ~ from mice, rats, dogs, and rabbits, and surgical pathology specimens of salivary glands from humans. In aqueous-acid extract~ of salivary glands, a large IRG, probably a proglucagon, was discovered. 7'~ This material is primarily present in the submaxillary glands of rodents but is present in measurable amounts in the other salivary glands and in the submaxillary glands of man.