What is glucagon and where is it made?
Glucagon is a 3.5 kDa linear polypeptide of 29 amino acids spliced from a 179 amino acid polypeptide that is expressed in the A cells of the Islets of Langerhans in the pancreas; the upper gastrointestinal tract in the L cells; and also in the brain. In the brain and L cells it is spliced into two glucagon like polypeptides (GLP1 & 2) which stimulate insulin secretion. Also made from the 179 amino acid polypeptide is oxyntomodulin that inhibits gastric acid secretion. In the A cells it is spliced into glucagon. Glucagon release is stimulated by exercise. Glucagon only comes into play in late exercise when the blood glucose is at critical point. As such, glucagon is only of importance in endurance training and starvation as this is when the demand for energy exceeds the intake and the various mechanisms discussed below come into play. What does it do? Glucagon is an endocrine hormone that mobilizes the body s energy stores. It stimulates glycogenolysis, gluconeogenesis, lipolysis, prote
