GI Hormones

Question 1

G Cells

Answer 1

Locations: Antrum*, Duodenum

Things That Increase Secretion:
- amino acids
- peptides
- gastric distension
- increased pH
- parasympathetic (using GRP)

Receptor (GPCR):
CCK2 (Gq)
(CCK-B)

Actions:
*Stomach

parietal (oxyntic) cells
- increases HCl secretion
- increases intrinsic factor (IF)

chief cells
- increases pepsinogen
- increase gastric lipase

mucosal cells
- trophic

ECL cells
- increases histamine release

Question 2

ECL/Mast Cell

Answer 2

Locations: Gastric glands, GI mucosa

Things That Increase Secretion:
- gastrin
- parasympathetic
- gastric distension

Receptor (GPCR):
H2 (Gs)

Actions:
*Stomach

parietal (oxyntic) cells
- increases HCl secretion
- increases intrinsic factor (IF)

chief cells
- increases pepsinogen
- increases gastric lipase

Question 3

I Cell

Answer 3

Locations: Duodenum, Jejunum

Things That Increase Secretion:
***via CCKRP (from enterocytes)
fatty acids
amino acids
peptides

monitor peptide
(released from pancreas into the pancreatic duct due to vagal stimulation of pancreatic acinar cells)

Receptor (GPCR):
CCK1 (Gq)
(CCK-A)

Actions:
*Pancreas
acinar cells
-increases enzyme release

ductal cells
- potentiates HCO3 secretion by secretin

*Gall bladder
causes contraction

*Sphincter of Oddi
causes relaxation (via NO)

*Gastric emptying
slows/delayed

*CNS
increases satiety
activates vagal afferents
(parasympathetic activation)

Question 4

S Cell

Answer 4

Locations: Duodenum, Jejunum

Things That Increase Secretion:
- low pH* (< 4.0)
- fatty acids

Receptor (GPCR):
SCTR (Gs)

Actions:
Pancreas
- ductal cells
increases HCO3 secretion
- acinar cells
potentiates enzyme release by CCK

*Bile duct
increases HCO3 secretion

*G cells
decreases gastrin release

*Gastric emptying
slows/delayed

Question 5

D Cell

Answer 5

Locations:
Stomach
Small intestines
Pancreas

Things That Increase Secretion:
low pH (< 4.0)
fatty acids
amino acids
peptides

Receptor (GPCR):
SSTR (Gi)

Actions:
Stomach
G cells: decreases gastrin release
parietal (oxyntic) cells:
decreases HCl secretion
decreases intrinsic factor (IF)
chief cells
decreases pepsinogen
decreases gastric lipase

Duodenum
I cells
decreases CCK release

Pancreas
acinar cells
decrease enzyme release
B (b) cells
decreases insulin release
A (a) cells
decreases glucagon release

Gall bladder
decreases contraction
(mostly due to decreased CCK)

Question 6

K Cell

Answer 6

Locations: Duodenum, Jejunum

Things That Increase Secretion:
glucose
fatty acids

Receptor (GPCR):
GIP-R (Gs)

Actions:
Pancreas
B (b) cells
increases insulin release

Gastric emptying
slows/delayed

Question 7

M Cell

Answer 7

Locations: Duodenum, Jejunum

Things That Increase Secretion:
fasting
(>1.5 hours)

Receptor (GPCR):
Motilin-R (Gq)

Actions:
Migrating Motor Complex (MMC)
peristaltic sweep
- stomach to ileocecal valve
relaxes pyloric sphincter