Renal Tubular Transport Mechanism II Flashcards
Where does the largest amount of Na+ get reabsorbed?
Proximal convoluted tubule (70%)
Why does Na+ osmolality stay the same along the proximal tubule?
Water follows it wherever it goes
What pumps Na+ at the basolateral membrane?
Na+/Cl- ATPase pump
How does Na+ enter the apical membrane?
Downhill gradient
What is important to note about water movement in the PCT?
Water is reabsorbed via osmosis through aquaporins, this causes an increase in solute concentrations left behind allowing them to be reabsorbed down their gradients
What various ions pass via paracellular route?
Cl-
Ca2+
K+
Urea
What pumps glucose in the apical membrane?
SGLT2
What pumps glucose in the basolateral membrane?
GLUT2
What pumps HCO3- in the basolateral membrane?
Na+/HCO3- cotransporter
What way can Na+ move across the apical membrane TAL?
Solute symporters
Na-H exchanger
Na+ paracellular movement
Transepithelial electrochemical driving force in proximal tubule S1 and S3:
S1: -3mV
S3: +3mV
(stronger movement back in S3)
What does CFEX pump do?
Pumps chlorine in and bases out across apical membrane to tubule lumen where they are protonated and brought back into the cell
What does KCC pump do?
K+ Cl- cotransporter
What type of transport takes place in the thin loops of Henle?
Paracellular Na+
Where are the NKCC2 channels found?
Thick ascending limb
What does the NKCC2 do?
Apical membrane reabsorption of Na+/K+/2Cl-
What diuretic inhibits NKCC2?
Furosemide
Bumetanide
Where is the NCC (Na/Cl cotransporter) found?
Distal convoluted tubule
What diuretics block the NCC?
Thiazides
Where are ENaC receptors found?
Collecting tubule principal cells
What diuretics block ENaC?
Amiloride
What does ENaC do?
Pump Na+ across the apical membrane
What is the major absorber of chloride in the S3 cells?
CFEX
What does CFEX absorb?
Cl-formate/oxalate/HCO3 and OH exchanger
What pumps Cl- across the basolateral membrane in the S3 cells?
CFTR
KCC (K/Cl cotransporter)
Cl- reabsorption in the TAL apical membrane and basolateral:
Apical: Na/K/Cl cotransporter Sodium/hydrogen exchanger Basolateral: N/K pump Cl- channel Cl-HCO3 exchanger
Cl- reabsorption in the DCT apical and basolateral:
Apical: Sodium/Cl- (NC-cotransporter)
Basolateral: N/K pump
Chloride channel
Cl- transport in the collecting tubule principle cell:
Paracellular diffusion
Cl- transport in the collecting tubule beta-intercalated cells apical and basolateral:
Apical: N/HCO3- exchanger
Basolateral: Cl- channel
