Pharmacology - gastric secretion

Question 1

gastric secretions of the gastric pit

mucus cells secrete x
parietal cells secrete x
ECN-like cells secrete x
G cells secrete x
D cells secrete x
Chief cells secrete x

gastric pit + gastric gland

these all promote the secretion of HCl, gastric acid

Answer 1

mucus + bicarbonate
HCl
Histamine
Gastrin
Somatostatin
pepsinogen

Question 2

the proton pump involves which 2 ions? moa? function?

responsible for secreting HCl into the stomach

Answer 2

H+/K+ ATPase

• The H⁺/K⁺-ATPase (proton pump) actively pumps H⁺ out into the stomach lumen.
• At the same time, K⁺ is pumped back into the parietal cell.
• Cl⁻ Also Moves into the Stomach
• Cl⁻ follows H⁺ into the stomach through Cl⁻ channels.This combines with H⁺ to form HCl (hydrochloric acid).

Question 3

Regulation of the Proton Pump (What Stimulates It?)

3 main stimulators

Answer 3

✅ Gastrin → Released from G cells (acts on CCKB receptors).
✅ Histamine → Released from enterochromaffin-like (ECL) cells (acts on H₂ receptors).
✅ Acetylcholine (ACh) → From vagus nerve (acts on M3 receptors).

🔹 These three increase cAMP or Ca²⁺ inside parietal cells → Activates the proton pump → More acid secretion.

Question 4

Proton Pump Inhibitors (PPIs) examples + INDICATIONS

Answer 4

Omeprazole, Pantoprazole

bind irreversibly to H⁺/K⁺-ATPase, preventing H⁺ secretion.

INDICATIONS:
- GERD
- pepti ulcers

Question 5

Histamine in response to xx is secreted by the xxx cells, binds to xx receptors, activating xxx, increasing xxx, to increase the number of xx, increasing/decreasing gastric acid secretion from yy cells

Answer 5

ACh
enterochromaffin like cells
H2 receptors in the GI
adenylyl cyclase
cAMP
proton pumps
INCREASING
parietal cells

Question 6

describe the action of ACh, and its impact on gastric acid secretion from parietal cells

Answer 6

ACh released from parasympathetic neurons
- binds to M3 ACh receptors
- activates PLC
- increases intra Ca2+
- increase number of proton pumps

INCREASES gastric acid secretion from parietal cells

Question 7

describe the action of gastrin and its effect on gastric acid secretion

released by:
binding to:
activating:
increasing number of :
effect on gastric acid secretion from parietal cells? :

Answer 7

released by: G cells
binding to: CCK2 receptors
activating: PLC
increasing number of : proton pumps
effect on gastric acid secretion from parietal cells? : INCREASE

Question 8

describe the action of SOMATOSTATIN and its effect on gastric acid secretion

Answer 8

released by: D cells
binding to: SST2R receptors
activating: DECREASING cAMP
increasing number of :
effect on gastric acid secretion from parietal cells? : DECREASING

**HOW DOES THIS WORK:
** - binding to SST2R receptors on enterochromaffin cells results in REDUCED HISTAMINE RELEASE + decreased acid secretion from the parietal cells —–> paracrine control

Question 9

NSAIDs
- examples (reversible, irreversible, non-selective, selective)
- indications
-side effects

Answer 9

⚠️ Side Effects:

1. Gastric ulcers, bleeding (due to COX-1 inhibition → less protective mucus in stomach).
2. Renal injury (less prostaglandins → reduced kidney blood flow).
3. Increased cardiovascular risk (except for aspirin, which reduces platelet aggregation).

2️⃣ Selective COX-2 Inhibitors (Lower GI Side Effects)
These selectively block COX-2, reducing inflammation without inhibiting stomach-protective COX-1.

1️⃣ Non-Selective COX Inhibitors (Block COX-1 & COX-2)
These inhibit both COX-1 (which protects the stomach & kidneys) and COX-2 (which causes inflammation & pain).

Question 10

Class + Indication + MOA + side effects of
- paracetamol
- clopidogrel
- misoprostol
- cimetidine
- omeprazole
- gaviscon
- ibuprofen

Answer 10

Question 11

effect of NSAIDs on gastric acid secretion + how is this mediated

Answer 11

promote HCl secretion

inhibit COX1, reducing prostaglandins

reduced prostaglandins LEADS TO –> histamine secretion from enterochromaffin cells

Question 12

cox 2 relates to

Answer 12

Function: Produces prostaglandins that mediate inflammation, pain, and fever.

but increase cardiovascular risk (by reducing PGI2, which normally prevents clotting).

Question 13

cox1 relates to

Answer 13

protect the stomach lining, regulate kidney function, and maintain platelet function.
🔹 Prostaglandins Produced:

PGE2, PGI2 (Prostacyclin) → Protects gastric mucosa.
Thromboxane A₂ (TXA2) → Promotes platelet aggregation (clotting).aglandins, protective function

– Inhibitory effects by eg NSAIDs, decrease prostaglandins, promoting HCl secretion, SIDE EFFECTS OF: gastric ulcers + blood in stool

Question 14

PPI example + moa+ indications + side effects

Answer 14

Omeprazole
irreversibly inhibtis H+/K+ ATPase pump
reduces HCl secretion

INDICATION: benign gastric aicd ulceration ++ GERD

side effects: increased stomach pH reduces defences agaisnt infection via the GI tract

Question 15

H2 receptor antagonist - example, moa, indications

Answer 15

Cimetidine
block H2 receptor –> reduces Hcl secretion
indication : gastric acid ulceration + NSAID associted gastric ulceration