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9 Cards in this Set

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What are Aquaporins?
Research on mice, rats and humans indicates that rapid diffusion of water across cell membranes depends on water channels made up of proteins called Aquaporins.
How many acquaporins have been identified?
Four acquaporins, 1, 2, 5 and 9 have been found in humans, and others have been found in rats. Most are found in the kidneys.
Where has aquaporin 9 been found?
It has been found in human leukocytes, liver, lung and spleen, and aquaporin 5 is found in human lacrimal glands.
Describe aquaporin 1?
It is localized in the proximal tubules. When it is destroyed in mice, proximal tubule water permeability is reduced 80%, and plasma osmolality increases to 500mosm/kg when the mice are subjected to dehydration, despite other aquaporins being intact.
Describe aquaporin 1?
It is localized in the proximal tubules. When it is destroyed in mice, proximal tubule water permeability is reduced 80%, and plasma osmolality increases to 500mosm/kg when the mice are subjected to dehydration, despite other aquaporins being intact.
What is Bartter's syndrome?
It is caused by defective transport in the thick ascending limb. It is characterized by chronic Na+ loss in the urine, with resultant hypovolemia causing stimulation of renin and aldosterone secretion without hypertension, plus hyperkalemia and alkalosis.
What is the pathogenesis of Bartter's syndrome?
It can be caused by loss of function mutations in the gene for any of four key proteins: the Na+-K+-2Cl- cotransporter, the ROMK K+ channel, the CIC-Kb Cl- channel, or barttin.
What is Barttin?
It is a recently described integral membrane protein that is necessary for the normal function of CIC-Kb Cl- channels.
The stria vascularis in the inner ear is responsible for maintaining the high K+ concentration in the scala media that is essential for normal hearing. TRUE/FALSE
TRUE. It contains both CIC-Kb and CIC-Ka Cl- channels.
Bartters syndrome associated with mutated CIC-Kb channels is not associated with deafness because the Clc-Ka channels can carry the load. However, both, types of Cl- channels are barttin dependent, so patients with Bartters syndrome due to mutated barttin are also deaf.