Pharmacology of gastric secretion

Question 1

What do mucus cells secrete?

Answer 1

Mucous and bicarbonate

Question 2

What do parietal cells secret?

Answer 2

HCL

Question 3

What do enterochramaffin-like cells secrete?

Answer 3

Histamine

Question 4

What do G cells secret?

Answer 4

Gastrin

Question 5

What do D cells secret?

Answer 5

Somatostatin

Question 6

Action of histamine?

Answer 6

• Secreted by enterochromaffin-like cells in gastric glands in response to stimulation by Ach
• Histamine binds to H2 receptors with subsequent activation of adenylyl cyclase
• Increase in cAMP increases number of proton pumps increasing gastric acid secretion from parietal cells

Question 7

What is histamine secreted by? And why?

Answer 7

Enterochromaffin-like cells in gastric glands in response to stimulation by ACh

Question 8

What does histamine bind to?

Answer 8

H2 receptors with subsequent activation of adenylyl cyclase- this increases no. of proton pumps, increasing gastric acid secretion from parietal cells

Question 9

What is ACh released by?

Answer 9

Parasympathetic cholinergic neurons

Question 10

What does ACh bind to?

Answer 10

Muscarinic M3 ACh receptors on parietal cells with subsequent activation of PLC (phopsholipase?)- The increase in extracellular Ca2+ evokes cell signalling pathways that increase the no. of proton pumps, increasing gastric acid secretion from parietal cells

Question 11

What is gastrin released by?

Answer 11

G cells

Question 12

What does gastrin bind to?

Answer 12

CCK2 receptors on parietal cells with subsequent activation if PLC
-Increase in extracellular Ca+ increases the no. of proton pumps, increasing gastric acid secretion from parietal cells

Question 13

What secretes somatostatin?

Answer 13

Secreted by D cells in gastric glands

Question 14

What does somatostatin bind to?

Answer 14

SST2 receptors inhibiting adenylyl cyclase, decrease in cAMP results in decreased gastric acid secretion from parietal cells

Question 15

What is the result of somatostatin binding to SST2R receptors or enterochromaffin-like cells?

Answer 15

Reduced histamine release and decreased gastric acid secretion from parietal cells

Question 16

What is the action of NSAIDs?

Answer 16

Disrupts the production of prostaglandins by inhibiting COX-1

Question 17

What effect does NSAIDS action have?

Answer 17

Reduced availability of prostaglandins results in histamine secretion from enter-chromaffin like cells= promoting HCL secretion from parietal cells

Question 18

Example of an NSAIDs?

Answer 18

Aspirin

Question 19

Diverse affects of NSAIDs and what can help them?

Answer 19

Peptic ulcers
Misoprostol (analogue of prostaglandin E1)
Side effects= abdominal pain and diarrhoea, also induces labour

Question 20

Side effects of misoprostol?

Answer 20

Abdominal pain and diarrhoea
Induces labour
-Helps peptic ulcers

Question 21

Examples of Proton pump inhibitors?(PPIs)

Answer 21

Lanzoprazole
Omeprazole
Pantoprazole

Question 22

What do PPIs do?

Answer 22

Irreversibly inhibit H+/K+ ATPase- reduces HCL secretion

Question 23

What are PPIs indicated for?

Answer 23

Benign gastric peptic ulceration and NSAID- associated gastric ulceration
Gastro-oesphageal reflux
Zollinger-Ellison syndrome

Question 24

Side effects of PPI?

Answer 24

Inreased stomach pH reduces defences against GI tract infections

Question 25

Examples of Histamine H2 receptors agonists?

Answer 25

Ranitidine
Cimetidine
Famotidine
Nizatidine

Question 26

Action of Histamine H2 receptors agonists?

Answer 26

Blocking H2 receptor eventually reduces HCL secretion, complete block of it produces rapid effect

Question 27

What are histamine H2 receptors indicated for?

Answer 27

Benign gastric acid ulceration

NSAIDs associated gastric ulceration

Question 28

What can cause peptic ulcers (bacteria)?

Answer 28

H. Pylori
Causes persistent inflammation that weakens mucosal barrier, eventually exposing sub-mucosa to attack from HCL and pepsin

Question 29

How to get rid of H. Pylori?

Answer 29

PPIs & antibiotics (clarithromycin & amoxicillan or metronidazole)