Gene models + nephron function (2) Flashcards
Semester 1 year 1
What is reabsorbed in the loop of Henle?
-sodium
-chloride
-water
-calcium
-magnesium
How does fluid move through the loop of Henle?
-arrives from proximal tubule
-moves down thin descending limb
-then moves up thin ascending limb
-then up thick ascending limb
What is the water permeability of the the thin descending limb and what is reabsorbed here?
-very water permeable
-water moves out
-nothing reabsorbed
What is the water permeability of the the thin ascending limb and what is reabsorbed here?
-not very water permeable
-permeable to sodium + chloride
-they move out
What is the water permeability of the the thick ascending limb and what is reabsorbed here?
-water impermeable
-permeable to sodium + chloride
-they move out
What protein channels are on which membranes of the cells of the thick ascending limb (TAL)?
On apical membrane:
-NKCC2
-ROMK (Kir1.1)
On basolateral membrane:
-ATPase
-Kir1.1
-CLCK
-Barttin
How does the protein NKCC2 work?
-1 Na+, 2 Cl-, 1 K+ bind to the protein
-causes conformational change
-ions released into intracellular fluid environment
-works due to Na+ grad. from ATPase
How does the sodium that enters via NKCC2 leave?
-via ATPase
-net Na+ reabsorption
How does the chloride that enters via NKCC2 leave?
-via CLCK on basolateral membrane
-net Cl- reabsorption
What is Barttin?
-a beta subunit (accessory protein)
-regulates CLCK channel
-in absence of Barttin, CLCK doesn’t work
How does the potassium that enters via NKCC2 leave?
By Kir1.1
Why does NKCC2 not work if potassium isn’t recycled by Kir1.1?
-potassium isn’t recycled
-results in low K+ conc. on apical membrane side
-wouldn’t be able to reabsorb Na+ or K+
How are calcium and magnesium reabsorbed?
Paracellular transport
Is Bartter’s syndrome recessive or dominant?
Recessive
What are the symptoms of Bartter’s syndrome?
-salt wasting (losing sodium + chlorine in urine)
-polyuria (excreting higher urine vol.)
What do individuals with Bartter’s syndrome have?
-hypotension (due to excreting water that would remain in blood)
-hypokalaemia
-metabolic alkalosis
-hypercalciuria (high Ca2+)
How many types of Bertter’s syndrome are there?
5 types
What do loop diuretics do?
-increase water loss in urine
-treatment for high blood pressure
What reabsorption occurs in the early distal tubule?
-sodium
-chloride
-magnesium
How does reabsorption occur across early distal tubule cells?
-sodium potassium ATPase on basolateral membrane decreases intracellular sodium
-Cl- + Na+ move in using NCC proteins on apical membrane
-potassium recycled using protein on basolateral membrane
-Mg2+ + Ca2+ ion enter via proteins on apical membrane + lost via proteins on basolateral membrane
How do thiazide diuretics work on the NCC protein?
-block sodium + chloride co-transporter, preventing their reabsorption
-reduces water reabsorption
What are thiazide diuretics used to treat?
High blood pressure
Is Gitelman’s syndrome dominant or recessive?
Recessive
What are the symptoms of Gitelman’s syndrome?
-salt wasting + polyuria
-hypotension
-hypokalaemia
-metabolic alkalosis
-hypocalciuria
