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Pathway Description
Pancreas Function - Alpha Cell
Homo sapiens
Physiological Pathway
Alpha cells are a type of islet cell found in the pancreas that release glucagon. Glucagon counteracts insulin and functions to maintain glucose homeostasis when detected glucose levels are low. Glucagon is contained in granules in the cell as a reserve ready to be released. Extracellular glucose levels and ion channels regulate the secretion of glucagon. Glucose undergoes glycolysis to increase ATP in the cell. The moderate activity of potassium ATP channels causes the membrane potential to be around -70mV. The alpha cell then becomes electrically active due to the closure of potassium channels. The cell membrane becomes depolarized due to voltage dependent sodium, potassium and calcium channels. This causes an increase in action potentials and opens voltage gate calcium channels causing an increase of calcium into the cell. This triggers the exocytosis of glucagon from the cell. Conversely, an increase in extracellular glucose leads to an increase in ATP production and inhibition of potassium ATP channels. The membrane depolarizes to a membrane potential that inactivates voltage dependent calcium channels. This results in decreased intracellular calcium and inhibits exocytosis of glucagon.
References
Pancreas Function - Alpha Cell References
Briant L, Salehi A, Vergari E, Zhang Q, Rorsman P: Glucagon secretion from pancreatic alpha-cells. Ups J Med Sci. 2016 May;121(2):113-9. doi: 10.3109/03009734.2016.1156789. Epub 2016 Apr 4.
Pubmed: 27044683
Gaisano HY, Macdonald PE, Vranic M: Glucagon secretion and signaling in the development of diabetes. Front Physiol. 2012 Sep 4;3:349. doi: 10.3389/fphys.2012.00349. eCollection 2012.
Pubmed: 22969729
Quesada I, Tuduri E, Ripoll C, Nadal A: Physiology of the pancreatic alpha-cell and glucagon secretion: role in glucose homeostasis and diabetes. J Endocrinol. 2008 Oct;199(1):5-19. doi: 10.1677/JOE-08-0290. Epub 2008 Jul 31.
Pubmed: 18669612
Vignali S, Leiss V, Karl R, Hofmann F, Welling A: Characterization of voltage-dependent sodium and calcium channels in mouse pancreatic A- and B-cells. J Physiol. 2006 May 1;572(Pt 3):691-706. doi: 10.1113/jphysiol.2005.102368.
Pubmed: 16513675
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