What is the role of gastrin and where is it produced?

• A. It stimulates acid secretion by parietal cells and is produced by G cells in the stomach antrum
• B. It inhibits acid secretion by parietal cells
• C. It stimulates mucus production in the stomach
• D. It is produced by chief cells to digest proteins

Answer: (A)

Gastrin is a peptide hormone whose main job is to boost digestion by increasing gastric acid. It is released by G cells located in the stomach’s antrum, the lower part near the pylorus, in response to food residues, peptides, amino acids, and stomach distension (with some enhancement from vagal stimulation).

Once gastrin is in the stomach, it raises acid output by acting on parietal cells to secrete hydrochloric acid. It does this directly and also indirectly by stimulating enterochromaffin-like cells to release histamine, which further stimulates parietal cells. This acid helps activate enzymes like pepsinogen and creates the acidic environment needed for protein digestion. Gastrin release is kept in check by negative feedback from the acidity of the stomach, via somatostatin from D cells.

So, its role is to stimulate acid secretion by parietal cells, and it is produced by G cells in the stomach antrum.