Which hormone produced by the posterior pituitary (neurohypophysis) increases water permeability in the collecting ducts of the kidney by inserting aquaporin-2 channels?
Answer and explanation
Correct answer: C. Antidiuretic hormone (ADH or vasopressin)
- Step 1: ADH is synthesized in the hypothalamus and released from the posterior pituitary in response to high plasma osmolarity. Step 2. It binds to V2 receptors on principal cells, stimulating cAMP-mediated translocation of aquaporin-2 channels into the apical membrane. Answer: Antidiuretic hormone (ADH or vasopressin). Why not the others: Aldosterone increases sodium reabsorption via ENaC channels; ANP promotes natriuresis; PTH regulates calcium and phosphate.
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