Regulation of GI Function II Flashcards
The active hormone gastrin is generated from a
Prepropeptide
What are the two major forms of Gastrin?
G-34 (10%)
G-17 (85%)
The terminal 4-aa sequence of Gastrin has
Biological activity
Which two receptors have over 50% sequence homology?
CCK-1 and CCK-2
Has a 1000-fold affinity for CCK
CCK-1
Has a high affinity for both CCK and Gastrin
CCK-2/gastrin receptor
Regulates gastric acid secretion both directly and indirectly
Gastrin
Gastrin DIRECTLY stimulates gastric acid secretion by acting directly on
Parietal cells via CCK-2 receptors
Acts indirectly via enterochromaffin-like (ECL) cell mediated histamine release to stimulate parietal cells
Gastrin
Gastrin acts indirectly to stimulate parietal cells via
Enterochromaffin-like (ECL) cell-mediated histamine release
Vagal activation stimulates multiple responses to regulate
Acid secretion
Stimulates gastric motility, helping to propel the food bolus distally
Gastrin
Also stimulates mucosal proliferation
Gastrin
Due to gastrin stimulation, we see an increase in ECL number resulting in
ECL hyperplasia
Gastrin stimulates mucosal proliferation and this increases the number of
Parietal cells
What three things stimulate Gastrin secretion?
- ) Meals (proteins, peptides, AAs)
- ) High Gastric pH
- ) Vagal stimulation
What are the two types of vagal stimulation that stimulate gastrin release?
Gastrin-releasing peptide and Gastric distension
What are the 4 factors that inhibit gastrin release?
- ) Fasting
- ) Low gastric pH
- ) SOMATOSTATIN
- ) CCK
We can see dilation of gastric glands and elongated parietal cells as the result of
Long-standing PPI use
Has molecular forms that range in size from 4-83 amino acids
Cholescystokinin (CCK)
The predominant molecular form of CCK is
CCK-58
Concentrated in the proximal small intestine (and brain)
-Responsible for CCK secretion
I cells
CCK is mostly distributed and secreted in the
Duodenum and Jejunum