Question

A drug which inhibits carbonic anhydrase decreases 

A. Bicarbonate formation and reabsorption in the kidney. 

B. Plasma bicarbonate levels. 

C. Blood pH. 

D. Urinary loss of potassium ions. 

E. Urinary volume and pH. 

Answer 1

A. True Carbonic anhydrase in tubular cells catalyses the combination of CO₂ and H₂O to form H₂CO₃ which ionizes into H⁺ and HCO₃⁺  ions.

B. True This is determined mainly by renal bicarbonate formation. 

C. True This falls as the plasma bicarbonate level falls. 

D. False More K⁺ is secreted by the tubules in exchange for sodium since there are fewer H⁺ ions to compete with K⁺ in the sodium/potassium exchange pump. 

E. False Failure to reabsorb HCO₃ results in an osmotic diuresis of alkaline urine.