Mechanisms to Adjust Urine Concentration

Question 1

What percent of Na+ is reabsorbed in the PCT and what is the mechanism?

Answer 1

1) 67%

2) Na+/H+ exchanger

Question 2

What percent of Na+ is reabsorbed in the TAL and what is the mechanism?

Answer 2

1) 35-40%

2) Na+/K+/2 Cl-

Question 3

What is the Lumen potential difference of the PCT?

Answer 3

Positive (+ 5mV)

Question 4

What is the Lumen potential difference of the TAL?

Answer 4

Positive (+ 6- + 10 mv)

Question 5

What is the percent of Na+ reabsorption of the Early Distal tubule and what is the mechanism?

Answer 5

1) 5.0-8.0%

2) Na+/Cl- cotransport

Question 6

What is the overall lumen potential difference of late the distal tubule?

Answer 6

Negative (-70 mV)

Question 7

What is the mechanism for Na+ reabsorption in the late distal tubule?

Answer 7

Luminal Na+ membrane channels

Question 8

What is the lumen potential for the early distal tubule?

Answer 8

Positive (due to presence of leaky K+ channels)