Tuesday, July 19, 2016

GI Hormones: Cholecystokinin Pancreozymin

Hi everyone ! So this is the 3rd post in  the series of the hormones of the GIT.
Last post we discussed about the Zollinger Ellison syndrome as a result of  Gastrin.  This post we look at the 2nd member of the gastrin family. Cholecystokinin PZ
Hope you like it. ::)

Cholecystokinin Pancreo-Zymin
Produced by : I cells in mucosa of Upper SI.
Physiology of secretion :
○ Acts vis CCK A receptor. (Gastrin acts via CCK-B if you recollect)
○Pre-Pro-CCK fragmented into many parts.
○Multiple AA in each for, but same 5 AA at Carboxy terminal
○Also found in distal ileum and colon + Cerebral Cortex.

Functions : lots.
○Gall bladder motility (contraction - kinesis)
○Stimulates pancreatic enzyme secretion ; augments secretin's actions
○Trophic action on pancreas
○Inhibits gastric emptying
○Causes contraction of pyloric sphincter -->preventing duodenal content aspiration.
○CNS --> role in regulation of satiety/food intake, Anxiety.
So if you notice, this does way more things than its brother Gastrin. Now it might get a little tedious to remember. So think of it this way :
Cholecysto-kinin Pancreo-Zymin. So first part of the name is cholecysto = Gall bladder. Kinin=motility. So 1. GB motility. Next is Pancreozymin. So acting on the zymogen granules in pancreas to bring about 2. enzyme secretion. Now along with causing enzyme stimulation it'll also tell the pancreas to grow up , hence exerting a 3. trophic action. So far so good?
Now for all of this gall and pancreatic fluid to reach the intestines , the barrier of the Oddi sphincter needs to be passed. So it'll 4.relax this sphincter causing the secretions to flow freely into the gut.
This causes a lot of fluid to be present in the duodenum. Since this is in proximity to the pylorus, the pyloric sphincter will  have to be shut to prevent aspiration of alkaline duodenal stuff into the stomach, hence 5.pyloric sphincter constricts.
Finally, since it's modulating so much of the digestion , it's got receptors in the CNS that 6.stimulate/depress hunger based on the CCK levels (like more CCK indicates more food being gulped down)
I have no idea about the anxiety part. So we're gonna have to go with it. Lol.
Regulation :
○Factors that increase -->
□Luminal  : fatty acids (>10Carbon atoms) -as lipase from pancreas acts on lipids and gall fluid contains fat digestive bile acids + AA.
□Other : CCK-Releasing peptide (intestinal mucosa) + Monitor factor (pancreatic)
+ feedback b/w degradation and secretioPZ
○ CCK in the injectable form can be used as a diagnostic aid to check Gall bladder motility
○ CCK Antagonists -->
□Proglumide =Non Selective. Ulceroprotective effect. (Gut action). May increase analgesic property of Opioids and help reduce Tolerance to them (CNS Action).
□Lorglumide =Selective fir CCK A type. Gut action.
□Studies are on going to harness their potential as anti-anxiety or anorectics. (CNS actions)
Next post - The secretin family.
Hope you'll are finding this helpful. Let me know if you have any doubts or suggestions. Bye until then=)

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