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Friday 19 September 2014

Gastrin release from antral G cells is regulated by the following mechanisms:

- luminal regulation:

  • amino acids (particularly phenylalanine and tryptophan) are responsible for food-induced gastrin release.
  • acidity of the gastric content is another major factor (alkaline pH is stimulatory and acidic pH is inhibitory).

- H. pylori:

  • by producing an alkaline pH by acid-neutralizing ammonia catalyzed by the bacterial urease.
  • by production of stimulatory cytokines (interleukin-1 beta and TNF-alpha) released from the T lymphocytes and monocytes present in the gastric inflammatory infiltrate.
    another possible mechanism is through inhibition of somatostatin that normally provides an inhibitory feedback to gastrin release.

- Neural and peptidergic regulation:

  • gastrin release is stimulated by activation of preganglionic vagal fibers, and is resistant to atropine. Paradoxically, the intraluminal stimulation (by a protein meal) of gastrin release is inhibited by low doses of atropine.
  • Bombesin and bombesin-like peptide (GRP) potently stimulate gastrin release which thereafter results in acid secretion.