What is the mechanism of action of proton pump inhibitors (PPIs)?

• A. Block histamine receptors
• B. Inhibit H+/K+ ATPase in gastric parietal cells
• C. Neutralize stomach acid
• D. Stimulate mucus secretion

Answer: (B)

Proton pump inhibitors (PPIs) work by specifically inhibiting the H+/K+ ATPase enzyme located in the gastric parietal cells of the stomach lining. This enzyme is crucial for the final step in gastric acid secretion; by blocking this pump, PPIs effectively reduce the production of stomach acid. This mechanism leads to increased gastric pH, which can help in the healing of ulcers and managing conditions associated with excessive acid production, such as gastroesophageal reflux disease (GERD).

In contrast, blocking histamine receptors (as referenced in the first option) works through a different mechanism, primarily impacting histamine type 2 receptors that also play a role in acid secretion but are not affected by PPIs. Neutralization of stomach acid, mentioned in another option, typically refers to the action of antacids, which chemically neutralize the acid present but do not decrease its production. The stimulation of mucus secretion from the stomach lining, as noted in another choice, serves protective functions but does not influence the production of gastric acid directly. Thus, the specific mechanism of inhibiting the H+/K+ ATPase is what aligns directly with how PPIs function in the body.