15. Transport in the loop of Henle and distal tubule Flashcards
Thick descending limb: permeability
high
Thick descending limb: secretory and absorptive and active transport
Little secretory and absorptive ability
No significant active transport in either
direction
Thick ascending limb: main forces
The main force is the Na+/K+-ATPase pump then pumps sodium from the cell to the interstitium, and potassium from the interstitium to the cell, against the concentration gradient
Thick ascending limb: luminal side
On the luminal side Na+ can e reabsorbed due to the decrease of IC Na+. The excess potassium leaves passively via the K+ channel of the
basolateral side.
Thick ascending limb: important protein
The most important protein of the
ascending limb is the Na+/K+/2Cl- symporter found on the luminal side.
Thick ascending limb: extra info
TAL is impermeable to water = lumen becomes hypoosmotic
- Symporter protein is inhibited by furosemide (drug) = water and salt loss diuresis occurs
Distal convoluted tubule: Na+/Cl- symport protein
The Na+/Cl- symport protein of this segment absorbs further 5% of the filtered sodium on the luminal side in an electrochemically neutral way.
Distal convoluted tubule: Cl transport
The chloride is carried by a special K+/Cl- cotransporter protein into the interstitium
Distal convoluted tubule: regulation
The regulated transport of calcium starts in this section, which is directed primarily by the calcium saving effect of the parathormone (PTH).
Hormonal and pharmacological effects: In the distal convoluted tubule
PTH: Ca2+ reabsorption
Calcitonin: Ca2+ excretion
Both: phosphate excretion
Hormonal and pharmacological effects: In the proximal and distal convoluted tubule, and collecting ducts:
Carbonic anhydrase inhibitors
Hormonal and pharmacological effects: In thick ascending limb
Furosamide: Inhibitor of the Na+/K+/Cl- reabsorption
Hormonal and pharmacological effects: In the distal convoluted tubule:
o Thiazide: Inhibitor of Na+/Cl- symport
