Question:
Impaired function of aquaporins (water channels) results in which of the following conditions?
Impaired function of aquaporins (water channels) results in which of the following conditions?
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If the ADH-driven water channel fails, the kidney cannot concentrate urine.
Updated On: Jun 23, 2026
- Liddle syndrome
- Nephrogenic diabetes insipidus
- Cystic fibrosis
- Bartter syndrome
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The Correct Option is B
Solution and Explanation
Answer: Nephrogenic diabetes insipidus.
Step 1: Aquaporins are integral membrane water channels. In the kidney, aquaporin-2 (AQP2) in the collecting duct is inserted into the apical membrane in response to ADH (vasopressin) and allows water reabsorption.
Step 2: If the AQP2 water channel (or its ADH-V2 receptor signalling) is defective, the collecting duct cannot reabsorb water even when ADH is present. The kidney fails to concentrate urine, producing polyuria and dilute urine: nephrogenic diabetes insipidus.
Step 3: Why not the others. Liddle syndrome is from a gain-of-function ENaC sodium channel mutation. Cystic fibrosis is from a defective CFTR chloride channel. Bartter syndrome is from defective Na-K-2Cl transport in the thick ascending limb. None of these involve aquaporins.
Hence aquaporin dysfunction causes nephrogenic DI.
Ref: Guyton and Hall Textbook of Medical Physiology, 13e.
Step 1: Aquaporins are integral membrane water channels. In the kidney, aquaporin-2 (AQP2) in the collecting duct is inserted into the apical membrane in response to ADH (vasopressin) and allows water reabsorption.
Step 2: If the AQP2 water channel (or its ADH-V2 receptor signalling) is defective, the collecting duct cannot reabsorb water even when ADH is present. The kidney fails to concentrate urine, producing polyuria and dilute urine: nephrogenic diabetes insipidus.
Step 3: Why not the others. Liddle syndrome is from a gain-of-function ENaC sodium channel mutation. Cystic fibrosis is from a defective CFTR chloride channel. Bartter syndrome is from defective Na-K-2Cl transport in the thick ascending limb. None of these involve aquaporins.
Hence aquaporin dysfunction causes nephrogenic DI.
Ref: Guyton and Hall Textbook of Medical Physiology, 13e.
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