Which substances amplify the acid secretion stimulated by gastrin in the stomach?

• A. Secretin and cholecystokinin
• B. Histamine and acetylcholine
• C. Epinephrine and norepinephrine
• D. Somatostatin and gastrin-releasing peptide

Answer: (B)

Gastrin-stimulated acid secretion is potentiated by two other mediators that act in different ways to boost the parietal cell’s output. Histamine, released from enterochromaffin-like cells in response to gastrin, binds to H2 receptors on parietal cells and increases cAMP, which markedly enhances acid production. Acetylcholine, from parasympathetic nerves, directly stimulates parietal cells via muscarinic receptors and also promotes gastrin release, further raising acid secretion. Together, they amplify the acid response beyond what gastrin would achieve alone.

The other substances don’t fit because they either inhibit acid secretion or don’t enhance gastrin’s effect: secretin and cholecystokinin tend to suppress or have little to no potentiating effect on gastric acid; epinephrine and norepinephrine generally inhibit gastric secretion; and somatostatin inhibits acid secretion, while gastrin-releasing peptide mainly increases gastrin release rather than directly boosting acid secretion.