8. Renal Transport Mechanisms – NaCl and Water Absorption along the Nephron Flashcards
What percentage of water and sodium is reabsorbed in the proximal convoluted tubule?
65 to 70%
What is the primary player in resorption?
Na/K ATPase
What is the advantage of taking a paracellular route?
The paracellular route does not require energy.
Where is the Na/K ATPase pump physically located?
In the basolateral membrane
What form of cellular transport is utilized in the reclamation of bicarbonate?
Trans-cellular
What 2 actions are completed by carbonic anhydrase in the reclamation of bicarbonate?
- The initial conversion of bicarbonate and hydrogen into carbonic acid
- The conversion of carbonic acid back into bicarbonate and hydrogen within the cell
What form of cellular transport is utilized in chloride reabsorption?
How does this occur?
Paracellular movement
More water than chloride is the absorbed in the 1st half of the proximal tubule, so the concentration of chloride increases. This creates a gradient for passive movement of chloride paracellularly.
Do we see more water transport in the thin descending limb of the loop of Henle, or the thick ascending limb of the loop of Henle?
Water flows freely out of the thin descending limb of the loop of Henle through both aquaporin proteins and loose junctions.
The thick ascending limb is impermeable to water, it has both tight junctions and a lack of aquaporin.
Where do we find aquaporin I proteins in the nephron?
In the proximal tubule, as well as in the thin descending limb of the loop of Henle.
Where do we find aquaporin II proteins?
In the collecting duct and late distal tubule.
What type of water movement is allowed in the collecting duct and late distal tubule?
Transcellular water movement only:
there are tight junctions, but they are also aquaporin II channels.
What is the main glucose transporter (the glucose transporter that is responsible for the majority of glucose)?
SGLT2
What transporter did we talk about as a common target for diabetic drugs?
SGLT2
Approximately how much water is absorbed by the descending loop of Henle?
15% of water filtered is through the descending loop of Henle
How is the descending loop of Henle able to concentrate solutes in the tubular fluid?
By re-absorbing water, but being impermeable to sodium chloride.