A 40-year-old male comes with complaint of indigestion and decreased appetite. He has a history of being treated for duodenal ulcer 4 years back. Investigation reveals elevation of gastrin levels. Which of the following statement is true regarding gastrin?
Ans: D (It gets stimulated by endolumina I peptides in stomach) Ref: Ganong's Review of Medical Physiology. 21st ed and Khurana Textbook of Medical Physiology By Khurana, pg: 605Explanation:GASTRINGastrin is secreted into the blood circulation and NOT into gastric juice.It reaches stomach through the arterial circulation.Stimulates secretory activity of parietal and chief cells.SourcesG cells - Antral mucosa (Most important source) -- Also called APUD cells.TG cells - found throughout the stomach and small intestine.Pancreatic islets in fetal life.Anterior and intermediate lobes of pituitary gland, hypothalamus, medullar oblongata, vagus and sciatic nerves.TypesG17, 14 and G34.FunctionsStimulates Gastric acid / HCI secretion from parietal cells.Stimulates HCI secretion by stimulating secretion of histamine from the enterochromaffin like cells (ECL) present in body of stomach.Stimulation of pepsin secretion.Stimulates growth of stomach and intestinal mucosa (Trophic action).Increases gastric and intestinal motility.Increases pancreatic secretion of Insulin and Glucagon but only after a protein meal.The functions of gastrin in the pituitary gland, brain and peripheral nerves are unknown.Control of Gastrin SectionFactors Stimulating Gastrin StimulationVagaf StimulationIncreases gastrin release through gastrin releasing peptide (GRP) and not through neurotransmitter ACHBecause of this reason, anti- muscarinic blocker atropine does not affect release of gastrin from G cellsDistension of Pyloric antrumThrough intrinsic innervation Proved by Heidenhain pouchProducts of protein digestionPeptides, amnioacidsCalcium Epinephrine Alcohol Coffee Factors Inhibiting Gastrin StimulationLow pH of gastric juice ( <3) -- Negative feedback mechanism.Somatostatin - Released by D cell.Secretin.Gastric Inhibitory Peptide (GIP)Vasactive intestinal peptide (VIP).Glucagon.Calcitonin. Control of gastrinsection | | | Stimuli increasinggastrin section Stimuli decreasinggastrin section || | | | |Luminal* Peptides and aminoacids* Distension Neural* Increased vagal discharge viaGRP* Calcium* Epinephrine Luminal* Acid* Somatostatin Blood Borne* Secretin* GP* VIP*Glucagon*Calcitonin
Secreted by parietal cells of stomach
Secreted by alpha ceils of pancreas
Decreases bicarbonate content in pancreatic secretion
It gets stimulated by endoluminal peptides in stomach
G.I.T.