Pharmacology of Gastric Acid Secretion

Question 1

Explain the process of HCl being secreted into the lumen

Answer 1

CO2 + H20 --> H2CO3 by CA
Splits to form H and HCO3
H moves into the lumen via H/K ATPase
HCO3 moves out via Cl/HCO3 excahnger
ClK symporter brings CL into the lumen

Question 2

List the cells in the gastric glands

Answer 2

Enterochromaffin - secrete histamine
Chief cells - secrete pepsiogen
Parietal cells - secrete HCl
D cells - secrete somatostatin
G cells - secrete gastricn
Mucous cells - secrete mucus and bicarbonate

Question 3

Explain the role of gastrin

Answer 3

Gastrin is released from G cells
Binds to Cholecystokinin receptors 
Activates PLC
Increases intracellular Calcium
Increases proton pump activation
Increases gastric acid

Question 4

Explain the role of aceylcholine

Answer 4

Acetylcholine released from parasympathetic nervous system
Binds to M3 receptors
Activates PLC
Increases intracellular Calcium
Increases proton pumps
Increases H secretion

Question 5

Explain the role of histamine

Answer 5

Histamine is released from enterochromaffin cells
Activates adenyl cyclase
Increase cAMP
Increase proton pumps
Increase hydrogen secretion

Question 6

Somatostatin

Answer 6

Released from D cells
Works on enterchromaffin cells
Preventing secretion of histamine 
Stops binding to adenyl cyclase
Stops cAMP
Reduces proton pumps
Decreases hyrdrogen

Somatostatin also binds to adenyl cyclase itself
Decreasesing cAMP
decreases proton pumps
Decreases H

Works on SST2R receptors

Question 7

Role of antacids

Answer 7

Reducing symptoms of excessive gastric acid by buffering HCl

Question 8

Mechanisms of NSAIDs

Answer 8

NSAIDs block the COX pathway
Stops the production of prostaglandin
Causes enterochromaffin to release histamine
Histamine works on adenyl cyclase to activate cAMP
Increases proton pumps
Increases H secretion

Question 9

What works in opposition to NSADIs

Answer 9

Misoprotol

Question 10

Side effects of misoprotolol

Answer 10

Abdominal pain, diarrhoea, can induce pregnancy

Question 11

Give examples of PPI

Answer 11

Omeprazole

Lansoprazole

Question 12

Give the mechanism of action of PPI

Answer 12

Irreversibly inhibits the H/KATPase decreases H secretion

Question 13

Uses of PPI

Answer 13

GORD
Zollinger Elison
Benign gastric acid ulceration
NSAID induced gastric acid ulceration

Question 14

Side effects of PPI

Answer 14

Increases stomach pH

Decreases stomach defensive mechanisms

Question 15

H pylori infection treatment

Answer 15

PPI + Clarithromycin + Metronidazole or Amoxycillin

Question 16

h2 antagonists examples

Answer 16

ranitidine

Question 17

H2 antagonist mechanism

Answer 17

Enterochromaffin cells - histamine
Histamine receptors on parietal cells blocked
Don’t they don’t stimulate adenyl cyclase to produce pKa
Decreases H being pumped into lumen by proton pump
Decreases hydrogen and therefore HCl

Question 18

When are H2 anatagonists used

Answer 18

NSAID peptic ulceration

Benign peptic ulcer