Proximal Tubule Flashcards
How much fluid is absorbed in PT?
2/3
What protein is highly abundant on the basolateral surface (4% total protein)
AQP1 so high water permeability.
What favours water uptake into the peritubular capillaries?
High oncotic pressure
What Na glucose cotransporter is on the apical surface?
SGLT2 (1Na and 1 glucose) works faster than SGLT1 but transports less glucose.
What transporter is responsible for 80% of total Na re absorption?
Na H cotransporter (1 Na in, 1 H out)
What is the effluxed H+ responsible for?
Acidifies Urine and mops up bicarbonate to form H2CO3
What way is Cl- reabsorbed?
Paracellularly or Via influx with HCOO- and efflux on the basolateral side with K.
What anion is needed to aid influx of PAH?
alpha ketoglutarate which is transported into the cell with Na.
What receptors allow the entry of proteins into vesicles for endocytosis?
Megalin/ Cubilin
What organelle are proteins degraded by?
Lysosomes
Why is Acetazolamide a weak diuretic?
As as soon as it has any effect the macula densa cells will detect increased salt and decrease GFR by negative feedback.
Why can Acetazolamide useful in mountain sickness?
As HCO3 will be lost in the urine it will generate a metabolic acidosis which will compensate the respiratory alkalosis and drive ventilation.
Why is Inulin freely filtered?
It is 5.5kDa
What does Inulin’s clearance amount represent?
GFR as all that is filtered appears in the urine.
Clearance =
filtered - absorbed + secreted
