Proximal Tubule

Question 0

What is reabsorbed in the proximal tubule?

Answer 0

60-70% of filtered load of sodium, water (aqp1, diffusion, on optic pressure) chlorine (diffusion and Cl/base anti porters) potassium (Na/k atlases, solvent drag) nearly all glucose, amino acids and organic solutes, bicarbonate, urea (diffusion)

Question 1

Normal values for GFR, ERPF, PCV, CO, RPF.

Answer 1

GFR 120ml/min
ERPF 600ml/min
PCV 40%
CO 5l/min 
RPF 1l/mim

Question 2

Mechanisms of sodium transport in the proximal tubule.

Answer 2

Na+/H+ exchanger, Na+ coupled with other solutes, diffusion, through tight junctions, Na enters cells alone

Question 3

Bicarbonate reabsorption.

Answer 3

H+ combines with HCO3- -> H2CO3
H2CO3 dissociates to CO2 and H2O, using carbonic anhydrase, diffuses in to cell.
Combine to H2CO3 again, dissociate to H+ and HCO3-
HCO3- reabsorbed, H+ secreted.