ADH renal action — FRCA Primary MCQ

Correct answer: D — ADH inserts aquaporin-2 channels in collecting ducts

ADH acts on V2 receptors to insert aquaporin-2 in collecting ducts. Raised PaCO2 lowers alveolar oxygen tension is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Central chemoreceptors respond to CSF hydrogen ion concentration is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Reduced haemoglobin lowers arterial oxygen content is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Closing capacity exceeding FRC causes airway closure is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physiology, the correct answer is usually the variable that best explains the observed change in the anaesthetised patient.

Reference: West's Respiratory Physiology; Ganong Review of Medical Physiology; Primary FRCA textbooks