indication

For treatment of severe hypoglycemia, also used in gastrointestinal imaging

pharmacology

Used in the treatment of hypoglycemia and in gastric imaging, glucagon increases blood glucose concentration and is used in the treatment of hypoglycemia. Glucagon acts only on liver glycogen, converting it to glucose through the release of insulin. It also relaxes the smooth muscles of the gastrointestinal tract.

mechanism of action

Glucagon binds the glucagon receptor, a G protein-coupled receptor located in the plasma membrane, which then initiates a dual signaling pathway using both adenylate cyclase activation and increased intracellular calcium. Adenylate cyclase manufactures cAMP (cyclic AMP), which activates protein kinase A (cAMP-dependent protein kinase). This enzyme, in turn, activates phosphorylase kinase, which, in turn, phosphorylates glycogen phosphorylase, converting into the active form called phosphorylase A. Phosphorylase A is the enzyme responsible for the release of glucose-1-phosphate from glycogen polymers. This yields glucose molecules to be released into the blood. Glucagon receptors are found in the liver, kidney, brain and pancreatic islet cells. The glucagon mediated signals lead to an increase in insulin excretion