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A. Site of production : G cells present in antral portion of stomach.

Other sites where gastrin is found:
Foetal islets of pancreas, pituitary gland (anterior and intermediate lobes), hypothalamus, medulla oblongata, vagus and sciatic nerves


  1. Stimulation of gastric acid and pepsin secretion
  2. Trophic action : gastrin stimulates the growth of mucosa of stomach, small and large intestines
  3. Stimulation of gastric motility
  4. Stimulation of insulin secretion; a protein meal (but not a carbohydrate meal) releases the amount of gastrin that is required to stimulate insulin secretion

C. Factors affecting gastrin secretion
Factors stimulating gastrin secretion

  1. Gastric distension e.g. by food
  2. Protein digestion products in the stomach viz. peptides and amino acids (the amino acids phenylalanine and tryptophan are very effective stimulants)
  3. Vagal stimulation; note that in the G cell, vagus releases the neurotransmitter GRP (or gastrin releasing peptide) and not acetylcholine; hence, the gastrin response to vagal stimulation is not abolished by atropine.
  4. Calcium, epinephrine

2. Factors inhibiting gastrin secretion

a. Acid :

Acid in the antrum inhibits gastrin secretion; this is another example of negative feedback control as shown below:

Gastrin → increases acid production but, acid feeds back to inhibit further gastrin secretion In pernicious anemia, there is damage to the acid-secreting cells of the stomach. Hence, the negative feedback inhibition of gastrin by acid is not there; thus, the gastrin levels are increased in such cases.

Acid inhibits gastrin secretion in two ways:

  • idirectly, by acting on G cells
  • indirectly, by releasing somatostatin (which is a potent inhibitor of gastrin secretion)

b. secretin, GIP, VIP, glucagons, calcitonin

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