Inhibition of pancreatic glucagon secretion during hyperglycemia could be mediated by (a) glucose, (b) insulin, (c) somatostatin, or (d) glucose in conjunction with insulin. To determine the role of these factors in the mediation of glucagon suppression, we injected alloxan while clamping the arterial supply of the pancreatic splenic lobe of dogs, thus inducing insulin deficiency localized to t...

Glucagon-producing pancreatic islet cells generate calcium-dependent action potentials. By the control of calcium influx through voltage-gated calcium channels, calcium is a tightly regulated second messenger in these cells. It is unknown whether calcium is a signal for glucagon gene transcription. Therefore, rat glucagon reporter fusion genes were transiently transfected into pancreatic islet ...

Impaired counterregulation during hypoglycemia in type 1 diabetes (T1D) is partly attributable to inadequate glucagon secretion. Intra-islet somatostatin (SST) suppression of hypoglycemia-stimulated α-cell glucagon release plays an important role. We hypothesized that hypoglycemia can be prevented in autoimmune T1D by SST receptor type 2 (SSTR2) antagonism of α-cells, which relieve SSTR2 inhibi...

In order to determine the role of glucagon in cold acclimation, the changes in glucagon receptor were investigated in white adipocytes from cold-acclimated rats by establishing a glucagon radioreceptor assay method for isolated white adipocytes. The following conditions were found to be appropriate for specific glucagon receptor binding assay; cell concentration of about 1 X 10(5) cells/ml, 15 ...

Background: Gastrointestinal (GI) endocrine cells produce many GI hormones that perform various physiological functions of the digestive system. Aims: We aimed to investigate the presence and distribution of immunoreactive (IR) endocrine cells to glucagon, somatostatin, cholecystokinin-8 (CCK-8), serotonin, secretin and histamine in the stomach of adult male Ne...

A method is described for the enzymatic synthesis of 5’-adenylyl imidodiphosphate labeled with a2P at the a! position (AMP-PNP-cx-~~P), an analogue of ATP containing nitrogen substituted for oxygen between the terminal phosphates. The nucleotide is only slowly hydrolyzed during incubation with rat liver plasma membranes and is a substrate for adenyl cyclase in these membranes. In the presence o...

BACKGROUND For automated prevention of hypoglycemia, there is a need for glucagon (or an analog) to be sufficiently stable so that it can be indwelled in a portable pump for at least 3 days. However, under some conditions, solutions of glucagon can form amyloid fibrils. Currently, the usage instructions for commercially available glucagon allow only for its immediate use. METHODS In NIH 3T3 f...

Glucagon is a potent stimulator of insulin release in the presence of a permissive glucose concentration, activating -cells in vitro via both glucagonand glucagon-like peptide-1 (GLP-1)–receptors. It is still unclear whether locally released glucagon amplifies the secretory responsiveness of neighboring -cells in the intact pancreas. The present study investigates this question in the perfused ...

The preproglucagon gene (Gcg) is expressed by specific enteroendocrine cells (L-cells) of the intestinal mucosa, pancreatic islet α-cells, and a discrete set of neurons within the nucleus of the solitary tract. Gcg encodes multiple peptides including glucagon, glucagon-like peptide-1, glucagon-like peptide-2, oxyntomodulin, and glicentin. Of these, glucagon and GLP-1 have received the most atte...

The effects of glucagon deficiency and excess on plasma concentrations of 21 amino acids were studied in six normal human subjects for 8 h. During glucagon deficiency, produced by intravenous infusion of somatostatin (0.5 mg/h) and insulin (5 mU/kg per h), amino acid concentration (sum of 21 amino acids) rose from 2,607 +/- 76 to 2,922 +/- 133 microM after 4 h (P less than 0.025). The largest i...