pharmacology of gastric secretion

Question 1

what does mucus cells secrete

Answer 1

mucus and bicarbonate

Question 2

what do parietal cells secrete

Answer 2

hydrochloric acid

Question 3

what do eneterchromaffin cells secrete

Answer 3

histamine

Question 4

what do chief cells secrete

Answer 4

pepsinogen

Question 5

what do D cells secrete

Answer 5

somatostatin

Question 6

what do G cells secrete

Answer 6

gastrin

Question 7

explain HCl secretion from gastric parietal cells

Answer 7

??? bitch you tell me

Question 8

explain histamine secretion

Answer 8

• it is secreted in the gastric glands by enterochromaffin cells in response to stimulation by Acetylcholine
• histamine binds to hydrogen receptors with subsequent activation of adenyly cyclase
• the increase in cAMP increases the number of proton pumps, increasing gastric acid secretion from parietal cells

Question 9

what release ACh

Answer 9

parasympathetic cholinergic neurones

Question 10

what does ACh bind to

Answer 10

muscarinic ACh receptors
-on parietal cells with subsequent activation of PLC

> the increase in intracellular calcium evokes cell signalling pathways that increase the number 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 cels with subsequent activation of PLC

> > increased intracellular calcium = more proton pumps = increased gastric acid secretion from parietal cells

Question 13

what is somatostatin secreted by

Answer 13

D cells in the gastric gland

Question 14

what does somatostatin bind to

Answer 14

SSTR receptors inhibiting adenylyl cyclase

> > the result =
a decrease in camp > decrease in gastric acid secretion

Question 15

result of somatostatin binding to SSTR receptors on enterochromaffin cells

Answer 15

> reduced histamine release
reduced decreased gastric acid secretion
from parietal cells

Question 16

effect of antacids

Answer 16

reduced the symptoms of excessive gastric acid secretion by buffering HCl

Question 17

examples of antacids

Answer 17

gaviscon
peptac

> use a sodium alginate ie NaHCO3 or CaCO3

Question 18

the action of NSAIDS on prostaglandins

Answer 18

> NSAIDS disrupt production of prostaglandins by inhibiting COX-1

-the reduced availability of prostaglandins results in histamine secretion from enterochromaffin cells > promoting HCl secretion from parietal cells

Question 19

what is misoprostol

Answer 19

> an analogue of prostaglandin E1

Question 20

when would you use misoprostol

Answer 20

> prophylaxis of NSIAD induced peptic ulcer

side effects include = abdominal pain and diarrhoea
**can also induce labour

Question 21

how do proton pumps work

Answer 21

they irreversibly inhibit H/K/ATPase pump > which reduces HCl secretion

Question 22

examples of PPIs

Answer 22

lansoprazole
omeprazole
pantoprazole

Question 23

when would PPIs be indicated

Answer 23

benign gastric acid ulceration and NSAID-associated gastric ulceration

> gastro-oesophageal reflux disease and Zollinger-Ellison syndrome

Question 24

side effects of PPIs

Answer 24

increased stomach pH

reduces defences against infection via the GI tract

Question 25

how do histamine H2 receptor antagonists work

Answer 25

block the H2 receptor which eventually reduces HCl secretion

Question 26

examples of histamine H2 receptor antagonists

Answer 26

ranitidine
cimetidine
famotidine
nizatidine

Question 27

when are histamine H2 receptors antagonists indicated

Answer 27

benign gastric acid ulceration and NSAID associated gastric ulceration

Question 28

how do treat an H. pylori infection ie peptic ulcer ?

Answer 28

PPIs + antibiotics (clarithromycin amoxicillin metronidazole)