Identification of glucagon in the gastrointestinal tract.

Abstract

A B S T R A C T Gel filtration studies on Bio-Gel P-10 columns of a 50-fold purified porcine duodenal extract revealed a main peak of glucagon-like immunoreactivity (GLI) in the 2,900 mol wt zone and a smaller peak in the 3,500 mol wt zone, the same zone as the pancreatic glucagon marker. Like pancreatic glucagon, samples of 3,500 mol wt material gave essentially identical measurements in radioimmunoassays employing the pancreatic glucagon-specific antiserum 30K and the GLI crossreacting antiserum 78J, whereas the 2,900 mol wt peptide gave 60-fold higher readings in the 78J assay. On disk gel electrophoresis, the 3,500 mol wt fraction, like pancreatic glucagon, migrated at pH 8.3, whereas the 2,900 mol wt peptide remained at the origin; at pH 4.7, the 2,900 mol wt peptide migrated while the 3,500 mol wt immunoreactive peptide and glucagon remained at the origin. Isoelectric focusing revealed the 3,500 mol wt moiety to have an isoelectric point (pI) of 6.2, the same as pancreatic glucagon, whereas the 2,900 mol wt peptide had an pI > 10. The glycogenolytic activity of the 3,500 mol wt peptide in the perfused rat liver did not differ significantly from glucagon, and its adenylate cyclase stimulating activity in partially purified liver cell membranes was comparable to that of glucagon; the 2,900 mol wt peptide had less than 20% of these activities. In samples of 3,500 mol wt material subjected to isoelectric focusing, adenylate cyclase-stimulating activity was confined to fractions containing 30K immunoreactivity with a pI of 6.2. In samples of 2,900 mol wt material subjected to isoelectric focusing, Dr. Sasaki's present address is The

Insulin releasing activity of gastrointestinal glucagon-like immunoreactive materials in perfused rat pancreas.

“…Furthermore, recent reports by Matsuyama and Foa (1974), Vranic et al(1974) and Sasaki et al(1975) suggest the presence of glucagon immunoreactivity, which reacted with antibody specific for pancreatic glucagon, in the gastrointestinal tract, especially abundant in the gastric fundus (Matsuyama et al, 1977). The biological activities of this material were reported to be close to those of pancreatic glucagon, as far as glycogenolytic and adenylate cyclase stimulating activities were concerned (Sasaki et al, 1975).…”

“…The biological activities of this material were reported to be close to those of pancreatic glucagon, as far as glycogenolytic and adenylate cyclase stimulating activities were concerned (Sasaki et al, 1975). However, no information regarding the insulinogenic activity of the material was available.…”

Identification of glucagon-producing cells (A cells) in dog gastric mucosa

“…This polypeptide has been clearly differentiated from the so-called "glucagon-like immunoreactivity" (GLI) (24), which is most abundant in the postduodenal small intestine (31). Since the oxyntic glandular mucosa of the canine stomach has been reported previously to contain cells resembling pancreatic A cells (19,3,4,28,13), the present study was designed to determine, by immunocytochemistry, whether these gastric cells are the source of gastric glucagon.…”

“…The glucagon-like activity first observed by Sutherland and De Duve in alcohol extracts of the upper gastrointestinal tract of the dog (30) is now attributed largely to the presence of a polypeptide with physicochemical, biological, and immunological properties indistinguishable from those of pancreatic glucagon (24). This polypeptide has been clearly differentiated from the so-called "glucagon-like immunoreactivity" (GLI) (24), which is most abundant in the postduodenal small intestine (31).…”

Evidence of glucagon biosynthesis involving protein intermediates in rat salivary glands

“…Gastrointestinal hormones have been detected in unforeseen locations [1] and peptides of neural origin have been found in pancreatic and gastrointestinal endocrine cells [2]. Glucagon, a hormone previously considered to be exclusively a product of pancreatic islets, has recently been detected in several extrapancreatic locations [3][4][5][6], where it could represent synthesised hormone, trapped or stored as an aggregate. However, cells similar to pancreatic A cells have been identified in the stomach [7,8], where large amounts of immunoreactive glucagon is released in response to specific stimuli [9][10][11].…”