pharmacology of gastric secretion Flashcards
what does mucus cells secrete
mucus and bicarbonate
what do parietal cells secrete
hydrochloric acid
what do eneterchromaffin cells secrete
histamine
what do chief cells secrete
pepsinogen
what do D cells secrete
somatostatin
what do G cells secrete
gastrin
explain HCl secretion from gastric parietal cells
??? bitch you tell me
explain histamine secretion
- 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
what release ACh
parasympathetic cholinergic neurones
what does ACh bind to
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
what is gastrin released by
G cells
what does gastrin bind to
CCK2 receptors on parietal cels with subsequent activation of PLC
> > increased intracellular calcium = more proton pumps = increased gastric acid secretion from parietal cells
what is somatostatin secreted by
D cells in the gastric gland
what does somatostatin bind to
SSTR receptors inhibiting adenylyl cyclase
> > the result =
a decrease in camp > decrease in gastric acid secretion
result of somatostatin binding to SSTR receptors on enterochromaffin cells
> reduced histamine release
reduced decreased gastric acid secretion
from parietal cells
effect of antacids
reduced the symptoms of excessive gastric acid secretion by buffering HCl
examples of antacids
gaviscon
peptac
> use a sodium alginate ie NaHCO3 or CaCO3
the action of NSAIDS on prostaglandins
> 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
what is misoprostol
> an analogue of prostaglandin E1
when would you use misoprostol
> prophylaxis of NSIAD induced peptic ulcer
side effects include = abdominal pain and diarrhoea
**can also induce labour
how do proton pumps work
they irreversibly inhibit H/K/ATPase pump > which reduces HCl secretion
examples of PPIs
lansoprazole
omeprazole
pantoprazole
when would PPIs be indicated
benign gastric acid ulceration and NSAID-associated gastric ulceration
> gastro-oesophageal reflux disease and Zollinger-Ellison syndrome
side effects of PPIs
increased stomach pH
reduces defences against infection via the GI tract
how do histamine H2 receptor antagonists work
block the H2 receptor which eventually reduces HCl secretion
examples of histamine H2 receptor antagonists
ranitidine
cimetidine
famotidine
nizatidine
when are histamine H2 receptors antagonists indicated
benign gastric acid ulceration and NSAID associated gastric ulceration
how do treat an H. pylori infection ie peptic ulcer ?
PPIs + antibiotics (clarithromycin amoxicillin metronidazole)
