Renal diluting segments and collecting systems

Question 1

Where on the nephron is water permeable?

Answer 1

Proximal tubule
Descending Loop of Henle

Question 2

Where on the nephron is water impermeable?

Answer 2

Ascending thin loop of Henle
Thick ascending loop of Henle
Early part of distal convoluted tubule

Question 3

Where is permeability to water regulated by ADH?

Answer 3

late part of distal convoluted tubule
Collecting tubule

Question 4

What aquaporin channel is found in the proximal tubule and descending loop of Henle?

Answer 4

AQP1
AQP7 - straight PT

Question 5

What aquaporin channel is found in the late distal convoluted tubule and collecting tubule?

Answer 5

Constitutive AQP3 and AQP4 on basolateral
Facultative AQP2 on apical

Question 6

Where is NaCl reabsorbed?

Answer 6

Thin and thick ascending limb

Question 7

What is the conc of fluid leaving TAL compared to plasma?

Answer 7

Dilute

Question 8

What is the driving force for transcellular transport in the TAL?

Answer 8

Basolateral Na+K+ATPase pump - maintains low intracellular Na+

Question 9

What mediates Na+ movement across apical membrane of the TAL?

Answer 9

NKCC2 symporter (also expressed by macula densa cells)

Question 10

What is essential for continued operation of NKCC2 symporter in the TAL?

Answer 10

K+ channels on apical membranes

Question 11

What else mediates Na+ movement across apical membrane of TAL?

Answer 11

Na+-H+ antiporter

Question 12

What other channels are present on the basolateral membrane of TAL?

Answer 12

Na+-HCO3- symporter
Cl- channels
K+Cl- channel
K= channels

Question 13

What drives paracellular reabsorption in the TAL?

Answer 13

Lumen-positive potential driven by K+ channels on apical membrane

Question 14

What cations does the TAL reabsorb?

Answer 14

Na+, K+, Mg2+ and Ca2+

Question 15

How do loop diuretics work?

Answer 15

Increase volume of excreted urine by blocking Na+ reabsorption at specific sites

Question 16

What loop diuretics block NKCC2?

Answer 16

Furosemide
Bumetanide

Question 17

What maintains the low intracellular Na+ in the early DCT?

Answer 17

Na+-K+-ATPase pump

Question 18

What mediates entry of NaCl across apical membrane in early DCT?

Answer 18

Na+-Cl- symporter

Question 19

How does Cl- leave the cell in early DCT?

Answer 19

Via Cl- channels on basolateral membrane

Question 20

What 2 cells are found in the late DCT and collecting ducts?

Answer 20

Principal and intercalated cells

Question 21

What is the MoA of principal cells?

Answer 21

Reabsorb Na+. Cl- and water
Secrete K+
Dependent on Na+-K+-ATPase pump on basolateral membrane

Question 22

What is the MoA of intercalated cells?

Answer 22

Reabsorb K+
Secrete H+ or HCO3-
Dependent on apical H+-K+ATPase pump

Question 23

What channels absorb Na+ on the apical membrane of the late DCT and collecting duct?

Answer 23

ENaC channels

Question 24

What is transported paracellularly in the late DCT and collecting ducts?

Answer 24

Cl-

Question 25

What regions of the kidney and low water permeability without ADH?

Answer 25

Outer medullary and cortical regions

Question 26

What triggers ADH production?

Answer 26

Hyper osmosis

Question 27

What does ADH bind to in the late DCT and collecting ducts?

Answer 27

V2 receptor on basolateral membrane

Question 28

What does the V2 receptor activate?

Answer 28

cAMP

Question 29

Where is the AQP2 water channel expressed?

Answer 29

Apical membrane of late DCT and collecting ducts

Question 30

How is water absorbed into the blood?

Answer 30

By osmosis via constitutively AQPs on basolateral membrane