skip to main content

ADH AQP2 Channels — FRCA Primary MCQ

Instant feedback + full explanation. One question, done properly.

HardPhysiology - RenalADH AQP2 ChannelsFRCA Primary

A patient with central diabetes insipidus receives desmopressin. Which change in a collecting-duct principal cell is expected before urine osmolality rises?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Increased apical AQP2 abundance with unchanged basolateral AQP3/4 expression acutely

The best answer is “Increased apical AQP2 abundance with unchanged basolateral AQP3/4 expression acutely”. Desmopressin acts through V2 receptors to increase apical AQP2 trafficking in principal cells, allowing water entry down the existing osmotic gradient; AQP3/4 are constitutively basolateral pathways. NKCC2 is in the thick ascending limb, ENaC is primarily aldosterone regulated, and SGLT2 belongs to the proximal tubule.

Reference: RCoA, Primary FRCA syllabus: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf; Collecting-duct principal-cell transport processes: https://pmc.ncbi.nlm.nih.gov/articles/PMC4284417/