Glucagon in Islet and Metabolic Regulation
This chapter reviews basic concepts in alpha-cell biology and glucagon physiology with an emphasis on how the processes are altered in disease states, particularly diabetes. It discusses relatively new findings that implicate glucagon in intra-islet signalling, hepatic protein metabolism, and energy balance, as well as descriptions of new uses for glucagon activity in drug development. The function of glucagon and other alpha-cell products is based in great part on the anatomy of the pancreatic islet. Glucagon secreted from islets in the pancreas collects in the portalvein, where concentrations are higher than other major vascular systems, and the liver is the primary target of glucagon signalling. The glucagon receptor is expressed by neurons throughout the central nervous system, including regions in the brain that are central to metabolic regulation. Glucagon moves into the brain from the circulation and administration of glucagon into the cerebroventricular system of rats suppresses food intake.
