Glucagon
Glucagon is a hormone found in the human body. It is secreted by the alpha cells of the endocrine portion of the pancreas. Glucagon is a 29-amino acid polypeptide. It is classified as a peptide hormone.
Secretion and Production
Glucagon is produced in and secreted from the alpha cells of the endocrine portion of the pancreas. Its production and secretion are stimulated by several factors, including decreased plasma glucose, increased catecholamines, increased plasma amino acids, the presence of acetylcholine, in response to signals from the sympathetic nervous system, and in response to the presence of cholecystokinin.
The main effect of glucagon is to oppose the action of insulin by raising blood-sugar to a normal level. Its other effects include reduction of the rate of synthesis of glycogen, promotion of the breakdown of protein, promotion of the use of fat as an energy source, and promotion of increased glucose uptake by muscle cells.
Another form of glucagon — gastrointestinal glucagon — is secreted into the blood when glucose is ingested. Its only effect is to promote the release of insulin.
Pharmacological Uses
Glucagon was first discovered in 1923 by Kimball and Martin. It has been synthesized, and it is commonly used as an intravenous drug to elevate blood-sugar levels in cases of extreme hypoglycemia. It is commonly used to treat diabetics whose blood sugar is so low that, if not treated immediately, could result in insulin shock.