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Gastrin

Gastrin. The ignition of stomach digestion. Background Information. Gastrin is a regulatory hormone that functions in the stomach. It regulates how much and when to secrete gastric acid and Pepsinogen, and the gastric mucosa. Origins of Gastrin.

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Gastrin

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  1. Gastrin The ignition of stomach digestion

  2. Background Information • Gastrin is a regulatory hormone that functions in the stomach. • It regulates how much and when to secrete gastric acid and Pepsinogen, and the gastric mucosa.

  3. Origins of Gastrin • Starts as “pre-pro-gastrin,” a 101 peptide sequence • Cleaves to 80, then 34, then 17 & 13 amino acid sequences from enzymatic cleaving • Only G34, G17, & G13 are functional. G17 is most prevalent and effective • All biological function is derived from the last four residues on terminal C, similarly with all cholecystokinin (cck) biomolecules

  4. Biochemical Control on Hormone Release • Stimulants: • Dearth of H+ ions (neutral pH) • Amino acids / peptide chains • Presences of Ca 2+ • Vagal Excitatory Fibers • Inhibitors: • Presence of H+ (low pH) • Production/ presence of Somatostatin • Vagal Inhibitory Fibers

  5. Gastrin's functions Upon ingestion of food and release of gastrin, the hormone binds with CCK-B receptors on the parietal cells CCK-Br’s are G-Protein coupled receptors which signal pathways due to conformational changes.

  6. Effects of gastrin on parietal cells • GPCR causes added permeability to Calcium ions through parietal cell membranes • Stimulates pathway to ultimately generate ATP for proton pump. • Reacts H20 and C02 to form bicarbonate ion HCO3- and protons H+, reactant for proton pump. • HCO3- diffuses out, replaced by Cl- • KCl(aq) moves to gastric mucosa through simple diffusion. • Proton pump moves K+ into the cell and H+, yielding HCl in the mucosa, thus supplying gastric acid

  7. Further function of gastrin: • Stimulation of gastric mucosal growth. • Indirectly stimulates parietal cells by stimulating ECL cells • Also stimulates chief cells, which signals for the production of pepsinogen

  8. References Andersson, Sven, ed.  Frontiers in Gastrointestinal Hormone Research.  Stockholm:  Almqvist & Wiksell, 1970. Hormonal and Neuronal Control of GIT.  U of Birmingham.  13 Apr 2006 <http://medweb.bham.ac.uk/research/toescu/Teaching/GIT/OutlineDetailsMeds.htm>. Pathophysiology of the Endocrine System.  Bowen, R. A. PhD.  2003.  State U. of Colorado.  13 Apr 2006 <http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/gi/gastrin.html>. Rehfeld, J.F., and E. Amdrup.  Gastrins and the Vagus.  New York:  Academic Press, 1979. Storch, Judy.  (2006, February, 23).  Human Digestive Tract.  Presented at RCSB PDB at Structural Anatomy Seminar, Piscataway, NJ.  Retrieved on April13, 2006, from http://rcsb-class.rutgers.edu/272/lectures/HumanDigestiveTract.pdf. Swiss-Prot Protein knowledgebase.  Human Gastrin.  2006.  13 Apr. 2006. Watson, Sue, and Robert Steele.  Gastrin Receptors in Gastrointestinal Tumors.  Austin:  R. G. Landes Company, 1993.

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