<prompt> In the presence of vasopressin the greatest fraction of filtered water is reabsorbed in which pa of the nephron?Proximal tubuleDistal tubuleLoope of HenleCollecting duct  <response>: The proximal tubule is responsible for reabsorbing 60 of filtered water irrespective of the presence or abscence of vassopressin. Ref: Harrisons principles of internal medicine, 18th edition, chapter: 277. 