Gastrin is a peptide hormone that is produced by G-cells located primarily in the gastric antrum and, to a lesser, degree the duodenum. The most important stimulator of gastrin release is food intake. Specifically, amino acids and short polypeptides stimulate the release of gastrin. Additionally, G-cells are stimulated by acetylcholine via cholinergic enervation through the vagus nerve. Gastric distention results in inhibition of gastrin release via vagal enervation. Gastric pH is also a factor, which affects gastrin secretion. Low intraluminal pH inhibits gastrin release whereas a higher pH potentiates gastrin secretion. Somatostatin, conversely, inhibits gastrin release. Gastrin stimulates the secretion of hydrochloric acid by the parietal cell, which is present in the gastric fundus. In turn, hydrogen ion inhibits gastrin release via a negative feedback loop. Thus, in states of achlorhydria such as pernicious anemia, hypergastrinemia is observed. Finally, gastrin has a trophic effect on gastric mucosa.

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