Physiology 2130 Lecture Notes - Lecture 44: Tandem Pore Domain Potassium Channel, Symporter, Endothelium
1 May 2018
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Lecture 044: Renal
Ascending Limb of the Loop Henle
Thin
● Na+ channel
○ on the apical/luminal membrane
○ Absorbeds sodium
Thick
● More metabolic active
● NKCC 2 transporter
○ On the apical membrane
○ Secondary transport
○ “Ion multiplier”
○ Can move many ion (4) at onces
○ 1 Na+, 1K+, 2 Cl-
■ Na+: favourable
● Drives the motion
■ Cl-: unfavourable
● Against the electrical gradient (inside of the cell is negative)
■ K+: unfavourable
● High in concentration inside the cell
○ Electroneutral movement
■ 2 positive and 2 negative ion
○ Need to have ALL the ions for the conformation change to occur
■ Thus, need a way to resupply the filtrate with K+ (recall K+ is low in the
filtrate)
●
● K+ leak channel
○ On the apical membrane
○ “Recycler” for K+
○ Resupply the filtrate with K+ so that there are enough K+ so that the NKCC 2
continues to work
● K+/Cl- symporter
○ On the basolateral membrane
○ K+ is high inside the cell, use this to drag Cl- out
● Cl- channel
○ On the basolateral membrane
○ Allows the Cl- to move out of the charge so that negative charges don’t build up
inside the cell
○ Favorale electrical and chemical movement
● Paracellular transport
○ Na+
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Document Summary
Can move many ion (4) at onces. Against the electrical gradient (inside of the cell is negative) Need to have all the ions for the conformation change to occur. Thus, need a way to resupply the filtrate with k+ (recall k+ is low in the filtrate) Resupply the filtrate with k+ so that there are enough k+ so that the nkcc 2. K+ is high inside the cell, use this to drag cl- out. Allows the cl- to move out of the charge so that negative charges don"t build up inside the cell. Moves to the interstitial space through gap junctions. Favourable due to the build up of negative charges due to the increase concentration of cl- in the isf. Early distal convoluted tubule acts like the ascending limb. Body is very concerned with blood calcium levels. Pth makes this protein undergo conformational faster. Or endocytosed out of the membrane (by adh)
