Thick Ascending Limb/Distal Tubule Renal Transport Flashcards
Is the Thick Ascending Limb permeable to water?
NO
What electrolyte is mostly reabsorbed at the Thick Ascending Limb?
Mg - Magnesium
Where does a majority of Mg reabsorption occur?
Thick Ascending limb
The Thick Ascending Limb is also an important site for reabsorption of Na, K, Ca, and Mg. What transporter on the apical border takes up Na, K, 2Cl?
NKCC2
NKCC2 is found where?
Apical border of Thick Ascending limb
What is taken up into the cell using NKCC2?
Na+
K+
2Cl-
At the Thick Ascending limb, once Na+ is in the cell, how does it get across the basolateral membrane to be reabsorbed?
Na+/K+ ATPase
At the Thick Ascending limb, once Cl- is in the cell, how does it get across the basolateral membrane to be reabsorbed?
Cl- channel
At the Thick Ascending limb, once K+ is in the cell, what are its 2 options?
- Leave the cell through a channel at the basolateral border and be reabsorbed
- Back leak through a ROMK channel at the apical border and re-enter the tubule lumen
If K+ inside the cell is going to back leak and re - enter the tubule lumen, what transporter will it use?
ROMK
NKCC2 pumps K+ inside the cell from the tubule lumen. ROMK can take K+ from inside the cell and put it back into the tubule lumen. What builds in the tubule lumen if ROMK does this?
K+ = POSITIVE CHARGES
As ROMK pumps more K+ back into the tubule lumen, the (+) charges increase. What does this cause?
Mg and Ca to be repelled out of the tubule lumen!!
- They diffuse paracellularly and are reabsorbed!
How are Mg2+ and Ca2+ reabsorbed at the Thick Ascending Limb?
Via Paracellular (btwn cells) diffusion caused by repelling the build up of K+ charges inside the tubule lumen due to ROMK on the apical border!
This is the site of LEAST amount of solutes being reabsorbed
Distal Tubule
Where is the most important site of regulation?
Distal Tubule
What are the cell types at the distal tubule?
- Principal cells
- Alpha - intercalated cells
- Beta - intercalated cells
What are the hormones involved in regulation at the distal tubule?
Aldosterone
ADH
What do the Principal cells at the Distal Tubule REABSORB?
Na+
Water
What do the Principal cells at the Distal Tubule SECRETE?
K+
What do the Alpha - Intercalated cells at the Distal Tubule REABSORB?
K+
HCO3-
What do the Alpha - Intercalated cells at the Distal Tubule SECRETE?
H+
What do the Beta - Intercalated cells at the Distal Tubule REABSORB?
H+
Cl-
What do the Beta - Intercalated cells at the Distal Tubule SECRETE?
K+
HCO3-
Through what transporter on the apical surface do Principal Cells REABSORB Na+?
ENaC
What hormone acts on ENaC transporters of Prinicipal cells?
Aldosterone!!
Causes more Na+ reabsorption
Where are principal cells, alpha and beta intercalated cells?
Distal Tubule
What are the effects Aldosterone has on Principal cells in the Distal Tubule?
INCREASES ENaC transporters for Na+ reabsorption into the cell on the apical border
INCREASES Na+/K+ ATPase for Na+ reabsorption on the basolateral border
== INCREASED Na+ reabsorption and K+ secretion!
This cell in the Distal Tubule reabsorbs Na+ and water, and it secretes K+
Principal cells
This cell in the Distal Tubule reabsorbs K+ and HCO3- and secretes H+
Alpha - intercalated cells
This cell in the Distal Tubule reabsorbs H+ and Cl- and secretes HCO3- and K+
Beta - intercalated cells
What transporter allows for alpha and beta - intercalated cells to exchange K+ and H+?
H - K ATPase
At the Distal Convoluted Tubule, what transporter on the apical side takes Ca++ into the cell?
TRPV5
Action of TRPV5 at the Distal Convoluted Tubule?
Uptakes Ca2+ into the cell
Where is TRPV5?
Distal Convoluted Tubule apical border
At the Distal Convoluted Tubule, what transporter on the apical side takes Na and Cl into the cell?
NCC “Thiazide Sensor”
Action of NCC transporter at the Distal Convoluted Tubule?
Uptakes Na and Cl into the cell
At the Distal Convoluted Tubule, what transporter exchanges Ca reabsorption for sodium to be pushed back into the cell on the basolateral border?
NCE
- Na Ca Exchanger
Action of NCE at the Distal Convoluted Tubule?
Reabsorbs Ca and puts Na back into the cell
Where is NCC?
Distal Convoluted Tubule apical border
Where is NCE?
Distal Convoluted Tubule basolateral border