Question

Pantoprazole acts by inhibiting
(A) Na-K ATPase
(B) H-K ATPase
(C) Na-H pump
(D) Na-Cl pump

• A. Na-K ATPase
• B. H-K ATPase
• C. Na-H pump
• D. Na-Cl pump

Hint:

Proton pump inhibitors (PPIs) like pantoprazole and omeprazole target the \(\text{H}^+/\text{K}^+\)-ATPase pump.
This is the final step in gastric acid secretion, making PPIs more effective than \(\text{H}_2\)-receptor antagonists (like ranitidine).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Gastric acid secretion by parietal cells is regulated by several neurohumoral pathways (histamine, acetylcholine, and gastrin).
These pathways converge on a final common pathway to pump protons (\(\text{H}^+\)) into the gastric lumen.

Step 2: Detailed Explanation:
Let us analyze the mechanism of action of pantoprazole:
- Proton Pump Inhibition: Pantoprazole is a substituted benzimidazole prodrug.
In the acidic environment of the parietal cell canaliculi, it is converted into its active sulfenamide form.
- Target Enzyme: The active form binds covalently to sulfhydryl groups on the \(\text{H}^+/\text{K}^+\)-ATPase enzyme (the proton pump), irreversibly inhibiting its activity.
- Because the \(\text{H}^+/\text{K}^+\)-ATPase pump is the final step in gastric acid secretion, inhibiting it blocks acid production regardless of the stimulus (histamine, gastrin, or acetylcholine).
- Evaluating other options:
- \(\text{Na}^+/\text{K}^+\)-ATPase (A): This is the sodium-potassium pump found in almost all animal cells, regulated by drugs like cardiac glycosides, not pantoprazole.
- \(\text{Na}^+/\text{H}^+\) exchanger (C) and \(\text{Na}^+/\text{Cl}^-\) cotransporter (D): These transport systems are located in renal and other tissues and are not the primary target of pantoprazole.

Step 3: Final Answer:
Pantoprazole acts by inhibiting the \(\text{H}^+/\text{K}^+\)-ATPase pump. This corresponds to option (B).