Renal Processing of Urea and Glucose Flashcards
Where are amino acids absorbed?
PCT
How is urea reabsorbed in the PCT?
Dragged with water
Where is urea secreted?
Into the thin portions of the loop of Henle
What secretes urea into the thin loops?
UT-A2 (urea transporter A2)
What uptakes AA in the PCT?
Solute transporter carriers (SLC)
Normal BUN levels?
7-18 mg/dL
What does urea cause in the medullary interstitial space?
Reabsorption of water
What affect does ADH/AVP have?
Causes UT-A1 to reabsorb urea from the collecting duct in order to maintain a gradient in the medulla between collecting ducts and the thin ascending loop to draw water out of the tubules
What moves urea across the collecting ducts membranes?
Apical: UT-A1
Basolateral: UT-A3
What secondary messenger is used by ADH/AVP to activate UT-A1?
cAMP
What absorbs glucose across the PCT apical and basolateral membrane?
Apical: SGLT (sodium glucose)
Basolateral: GLUT 1/2
What creates the gradient for sodium to be used in the apical SGLT?
Na/K ATPase
What can occur in excess glucose concentration in the PCT?
SGLT can become oversaturated
When does splay occur?
When SGLT are oversaturated
Why is splay a curve and not a straight line?
Due to the many SGLT receptors with different glucose tubular maximums in the various nephrons
What does SLC1A1 code for?
Excitatory amino-acid transporter 3 (EAAT3)
What are EAAT3 also known as?
High affinity glutamate transporters
What drives AA transport?
The negative cell charge
Where are oligopeptides absorbed?
PCT
DCT
What absorbs oligopeptides in the PCT and DCT respectively?
PCT: PepT1
DCT: PepT2
PepT1 vs PepT2:
PepT1: high capacity low affinity
PepT2: low capacity high affinity
What is needed for oligopeptides to be absorbed?
Sodium
General mechanism of protein reabsorption?
Bind to receptor then endocytosed through clathrin coated pit to lysosomes and digested
What takes up albumin from the PCT?
Megalin
Cubulin
What transports carboxylates on apical?
Na-dependent mono-di-tri-carboxylate transporters
What transports dicarboxylates on the basolateral side?
OAT1 and OAT3
How does OAT work?
Pumps dicarboxylates across the basolateral for an organic anion into the cell
