Endocrine Control of Endocrine Control of Gastrointestinal FunctionGastrointestinal Function

Jack L. Leonard 2004Jack L. Leonard 2004

HormoneHormone ActionAction Release siteRelease site Secretion stimulusSecretion stimulus

GastrinGastrin Gastric acid secretion Gastric acid secretion

Growth of oxyntic gland Growth of oxyntic gland

mucosamucosa

AntrumAntrumduodenumduodenum

Peptides, AAPeptides, AA

DistentionDistention

Vagal activityVagal activity

CCKCCK Gall Bladder contraction Gall Bladder contraction

Pancreatic juice secretion Pancreatic juice secretion

enzymeenzyme

bicarbonatebicarbonate

Pancreatic exocirne growthPancreatic exocirne growth

DuodenumDuodenum

JejunumJejunum

Peptides, AAPeptides, AA

Fatty acids>8CFatty acids>8CAcidAcid

SecretinSecretin Pepsin secretion Pepsin secretion

Pancreatic juice secretion Pancreatic juice secretion

enzymesenzymes

bicarbonatebicarbonate

Pancreatic exocirne growthPancreatic exocirne growth

DuodenumDuodenum Acidfat

GIPGIP Insulin secretion Insulin secretion

Gastric acid secretionGastric acid secretionDuodenumDuodenum

JejunumJejunum

Glucose, AAGlucose, AA

Fatty acidsFatty acids

GI HormonesGI Hormones

PeptidePeptide ActionAction Release siteRelease site SecretionSecretion

stimulusstimulus

MotilinMotilin Gastric andGastric and

duodenal motilityduodenal motilityDuodenumDuodenum

JejunumJejunum

UnknownUnknown

Pancreatic Pancreatic polypeptidepolypeptide

Pancreatic juice secretion Pancreatic juice secretion

enzymeenzyme

bicarbonatebicarbonate

PancreasPancreas ProteinProteinFatFat

GlucoseGlucose

EnteroglucagonEnteroglucagon unknownunknown IleumIleum Glucose

Fat

Candidate HormonesCandidate Hormones

PeptidePeptide ActionAction Release siteRelease site

VIPVIP Relaxes sphinctersRelaxes sphincters

Relaxes gut circular muscleRelaxes gut circular muscle

Stimulates intestinal secretionStimulates intestinal secretion

Simulates pancreatic Simulates pancreatic secretionsecretion

DuodenumDuodenum

JejunumJejunum

Bombesin or GRPBombesin or GRP

EnkephalinsEnkephalins

Stimulates gastrin secretionStimulates gastrin secretion

Stimulates smooth muscle Stimulates smooth muscle contractioncontraction

Inhibits intestinal secretionInhibits intestinal secretion

Gastric mucosaGastric mucosa

Muscosa and Muscosa and smooth muscle smooth muscle of GI tractof GI tract

NeurocrinesNeurocrines

Fed meatFed meat

11 22 33 44

HoursHours

Vo

lum

e V

olu

me

(ml/

15

(ml/

15

min

)m

in)

55

1010

1515

2020

2525

5050

150150

100100

totaltotal

cephaliccephalic

gastricgastric

intestinalintestinaltotaltotal

cephaliccephalic

gastricgastric

intestinalintestinal

Volume SecretedVolume Secretedduring first 2 hrsduring first 2 hrs

The Three Phases of Acid SecretionThe Three Phases of Acid Secretion

BombesinBombesin

++AcetylcholineAcetylcholine

++

SomatostatinSomatostatin--

++

gastringastrin

G-cellG-cell SomatostatinSomatostatincellcell

OxynticOxynticcellcell

sight, smellsight, smelltaste, chewingtaste, chewing

swallowingswallowingconditioned reflexconditioned reflex

++Vagal nucleusVagal nucleus

--

HH++

Cephalic PhaseCephalic Phase

ProteinProteindigestiondigestion

PeptidesPeptidesAminoAminoacidsacids HH++acetylcholineacetylcholine

gastringastrinVago-Vago-vagalvagalreflexreflex

bombesinbombesin

locallocalreflexreflex acetylcholineacetylcholine

StomachStomachdistentiondistention

Gastric PhaseGastric Phase

Absorbed amino acidsAbsorbed amino acids

Intestinal PhaseIntestinal Phase

IntestinalIntestinalEndocrineEndocrine

CellCell

Entero-Entero-oxyntinoxyntin

ProteinProteinDigestionDigestionproductsproducts

HH++

IntestinalIntestinalG CellG Cell GastrinGastrin

Factors Regulating Acid SecretionFactors Regulating Acid Secretion

Factors Regulating Acid SecretionFactors Regulating Acid Secretion

Conditioned stimuliConditioned stimuliSmell, tasteSmell, tasteChewingChewingSwallowingSwallowinghypoglycemiahypoglycemia

Vagus nerveVagus nerve

G cellG cellGastrinGastrin

GastrinGastrin

Acinar cellsAcinar cells

HH220 &0 &

HCOHCO33--

EnzymesEnzymesDuct cellsDuct cells

AcHAcHAcHAcH

Factors Regulating Acid Secretion (cont)Factors Regulating Acid Secretion (cont)

Vagus nerveVagus nerve(vagovagal reflex)(vagovagal reflex)

Parietal cellParietal cell

FatFatProteinProtein

HH++

Peptides + Amino acidsPeptides + Amino acids

E cellsE cells

CCKCCK

CCKCCK

SecretinSecretin

HH220 &0 &

HCOHCO33--

SecretinSecretinAcHAcH

AcHAcH AcinarAcinarcellscells

DuctDuctcellscells

EnzymesEnzymes

FatFatS cellsS cells

H+H+

Pancreatic Enzyme SecretionPancreatic Enzyme Secretion

Pre-PrandialPre-PrandialPancreasPancreas

Monitor peptideMonitor peptide

ChymotrypsinChymotrypsin

TrypsinTrypsin

Small intestineSmall intestine

Post-PrandialPost-Prandial

Food ProteinFood Protein

CCKCCK

Gut – Insulin SecretionGut – Insulin SecretionNeural reflexesNeural reflexes

00

100100

00

100100

10% glucose10% glucose

10% glucose10% glucose

5 min5 min

00 44 88minmin11 2020 4040

100100

5050

00

minmin

Insu

lin

Insu

lin ((

U/m

lU

/ml

Insu

lin

Insu

lin ((

U/m

lU

/ml

2020

4040Oral doseOral dose Intestinal doseIntestinal dose