Endocrine Control of Gastrointestinal Function Jack L. Leonard 2004

HormoneAction Release site Secretion stimulus Gastrin Gastric acid secretion Growth of oxyntic gland Growth of oxyntic gland mucosa mucosaAntrumduodenum Peptides, AA Peptides, AA Distention Distention Vagal activity Vagal activity CCK Gall Bladder contraction Pancreatic juice secretion Pancreatic juice secretion enzyme enzyme bicarbonate bicarbonate Pancreatic exocirne growth Pancreatic exocirne growthDuodenumJejunum Peptides, AA Fatty acids>8C Acid Secretin Pepsin secretion Pepsin secretion Pancreatic juice secretion Pancreatic juice secretion enzymes enzymes bicarbonate bicarbonate Pancreatic exocirne growth Pancreatic exocirne growthDuodenumAcid fat GIP Insulin secretion Insulin secretion Gastric acid secretion Gastric acid secretionDuodenumJejunum Glucose, AA Fatty acids GI Hormones

PeptideAction Release site Secretion stimulus stimulus Motilin Gastric and duodenal motility duodenal motilityDuodenumJejunumUnknown Pancreatic polypeptide Pancreatic juice secretion enzyme enzyme bicarbonate bicarbonatePancreasProteinFatGlucose Enteroglucagon unknown unknownIleumGlucose Fat Candidate Hormones

PeptideAction Release site VIP Relaxes sphincters Relaxes gut circular muscle Stimulates intestinal secretion Simulates pancreatic secretion DuodenumJejunum Bombesin or GRP Enkephalins Stimulates gastrin secretion Stimulates smooth muscle contraction Inhibits intestinal secretion Gastric mucosa Muscosa and smooth muscle of GI tract Neurocrines

Fed meat 1234 Hours Volume (ml/15 min) total cephalic gastric intestinal total cephalic gastric intestinal Volume Secreted during first 2 hrs The Three Phases of Acid Secretion

Bombesin + Acetylcholine + Somatostatin- +gastrin G-cell Somatostatincell Oxynticcell sight, smell taste, chewing swallowing conditioned reflex + Vagal nucleus - H+H+H+H+ Cephalic Phase

Proteindigestion PeptidesAminoacids H+H+H+H+ acetylcholine gastrin Vago-vagalreflex bombesin localreflexacetylcholine Stomachdistention Gastric Phase

Absorbed amino acids Intestinal Phase IntestinalEndocrine Cell Cell Entero-oxyntin ProteinDigestionproducts H+H+H+H+Intestinal G Cell Gastrin

Factors Regulating Acid Secretion

Conditioned stimuli Smell, taste ChewingSwallowinghypoglycemia Vagus nerve G cell Gastrin Gastrin Acinar cells H 2 0 & HCO 3 - Enzymes Duct cells AcH AcH

Factors Regulating Acid Secretion (cont) Vagus nerve (vagovagal reflex) Parietal cell FatProtein H + Peptides + Amino acids E cells CCK CCK Secretin H 2 0 & HCO 3 - Secretin AcH AcH Acinarcells Ductcells Enzymes Fat S cells H+

Pancreatic Enzyme Secretion Pre-Prandial Pancreas Monitor peptide Chymotrypsin Trypsin Small intestine Post-Prandial Food Protein CCK

Gut – Insulin Secretion Neural reflexes % glucose 5 min 048 min min Insulin (  U/ml Oral dose Intestinal dose