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In humans, the glomerulus can filter 180 L/day of fluid from
plasma, of which 90% (about 162 L) is returned to the circulation by reabsorption in the proximal tubule and descending
limb of the loop of Henle.
Most of the remaining 18 L is reabsorbed...
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353
In humans, the glomerulus can filter 180 L/day of fluid from
plasma, of which 90% (about 162 L) is returned to the circulation by reabsorption in the proximal tubule and descending
limb of the loop of Henle.
Most of the remaining 18 L is reabsorbed under the regulation of vasopressin (VP) in the cortical
and medullary collecting ducts.
Failure of this regulated pathway for water reabsorption in the collecting ducts results in
the production of copious amounts of dilute urine—a disease
known as diabetes insipidus (DI).
VP—the antidiuretic hormone—plays a multifaceted role in the urinary concentrating process in mammals by activating the type 2 VP receptor
(V2R), a G protein–coupled receptor (GPCR).
VP increases
collecting duct water permeability by increasing the plasma
membrane accumulation of a water channel, aquaporin-2
(AQP2), in principal cells.
It acts on thick ascending limbs
of Henle to stimulate NaCl reabsorption, which increases the
osmolality of the medullary interst
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