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Aquaporins of the Kidney and Water Homeostasis - Anatomy & Physiology (view source)
Revision as of 16:27, 11 August 2008
, 16:27, 11 August 2008no edit summary
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==The Ability of the Kidney To Alter the Water Content of the Body==
* Take a dog which weighs 20kg and is drinking normally. It will produce 0.5l of water per 24 hours.
* If the dog drinks excessively it can produce 8ml urine/min to compensate meaning a total of 11 litres per 24 hours
* If a dog is denied water the production drops to a tiny 0.15 litres per 24 hours
The reabsorption of water can occur paracellulary - the main method in the proximal tubule or transcellulary - the main method in the distal tubule and collecting duct.
* Contrary to popular belief diffusion of water accross lipid bilayers (transcellulary) is too slow for most physiological processes
* Aquaporins solve this problem
==What are Aquaporins==
==What are Aquaporins==
* Family of membrane channel proteins
* Family of membrane channel proteins
** Thanks to the gradient created by the hypertonic medulla which is present due to the countercurrent multiplier in the [[Loop Of Henle - Anatomy & Physiology| Loop of Henle]]
** Thanks to the gradient created by the hypertonic medulla which is present due to the countercurrent multiplier in the [[Loop Of Henle - Anatomy & Physiology| Loop of Henle]]
* This system allows both concentrated and dilute urine to be produced depending on ADH secretion and therefore the density of aquaporins in the principal cell membranes
* This system allows both concentrated and dilute urine to be produced depending on ADH secretion and therefore the density of aquaporins in the principal cell membranes
==Other Means of Water Homeostasis==
==Other Means of Water Homeostasis==
As well as the aquaporins in the distal tubule and collecting duct significant water reabsorption occurs in the [[Proximal Tubule - Anatomy & Physiology| proximal tubule]] and the [[Loop Of Henle - Anatomy & Physiology| Loop of Henle]] and is linked to the absorption of [[Sodium Homeostasis - Physiology| sodium.]]
As well as the aquaporins in the distal tubule and collecting duct significant water reabsorption occurs in the [[Proximal Tubule - Anatomy & Physiology| proximal tubule]] and the [[Loop Of Henle - Anatomy & Physiology| Loop of Henle]] and is linked to the absorption of [[Sodium Homeostasis - Physiology| sodium.]]