Download Kidney Transporters

PROXIMAL TUBULE
Substance
Glucose
Transport Mechanism
Tm Reabsorption (secondary
active transport)
Apical Membrane
SGLT2 and SGLT1 Na-glucose
co-transporters (specific for D
isomer)
Na-Pi co-transporter
Basolateral Membrane
-Na/K+ ATPase (Na+ gradient)
-Transporter to move glucose
out
-Na/K+ ATPase (Na+ gradient)
-Pi-anion co transporter
Inorganic Phosphate
Tm Reabsorption (secondary
active)
Amino Acids
Tm Reabsorption (secondary
active)
Tm Reabsorption (secondary
active)
Non-Tm reabsorption
Basic, acidic and other (3
types) transporters
-Na-H exchanger (NHE-3)
secretes H+ at apical
membrane by secondary
active transport
-H-ATPase secretes H+ at
apical membrane via primary
active transport
-Na/K+ ATPase (Na+ gradient)
-Na-3HCO3- co-transporter
Non-Tm reabsorption
-Reabsorbed between cells in
early PT (solvent drag)
-Reabsorbed through cells
late in PT
Non-Tm reabsorption
(passive)
Base/Anion-Cl- exchanger
coupled to Na/H+ exchanger
causes Cl- to enter cell
(tertiary active transport)
-Na/K+ ATPase (Na+ gradient)
-Cl- channel or bicarbonate
exchanger
Reabsorbed through or
between cells (solvent drag)
Organic Anions (PAH, uric
acid, radiologic contrast
media, furosemide, penicillin)
Tm secretion (tertiary active
transport)
Organic Cation
Tm secretion (secondary
active)
-MRP2 pumps anion out to TF
linked to NaDC1 which brings
alphaKG and 3 Na+ in
-electrogenic anion
transporter
-anion exchanger
-organic cation:H+ exchanger
puts OC into TF (H+ enters cell
down EC gradiet)
-Na/K ATPase prevents K+
from leaving cell down at
basolateral membrane
-OAT1 moves organic anion
into cell for alphaKG
-NaDC3- alphaKG back into
cell with 3 Na+
- Na/K ATPase
Metabolic Intermediates
Bicarbonate
Na and Cl
K+
-OCT brings cation into cell
down EC gradient
Regulation
-Kidney helps regulate Pi
levels by excreting Pi in the
urine when levels exceed
threshold
-PTH lowers Tm and increases
GFR, decreasing threshold
and increases excretion
-Carbonic anhydrase activity
(if low, will decrease
reabsorption)
-pCO2 (if increased, will
increase reabsorption)
-Amount of HCO3- filtered
(more filtered means more
reabsorbed)
-Catecholamines increase
proximal Na+ reabsorption
-ANF decreases Na+
reabsorption