Distal Tubule and Collecting Duct Genes

Question 1

What are the 2 cell types of the distal tubule?

Answer 1

• Principal

- Intercalated

Question 2

What are the two types of collecting duct cell types?

Answer 2

Principal and intercalated

Question 3

What are the two types of intercalated cell?

Answer 3

α and ß

α is acid-releasing and more present in Western, high-protein, diets

Question 4

What membrane channels are found on the basolateral side of a principal cell of the collecting?

Answer 4

Kir 2.3
AQP3
AQP4

Question 5

What membrane channels are found on the apical side of a principal cell of the collecting?

Answer 5

ENaC
ROMK
Aquaporin 2

Question 6

What does Kir2.3 transport?

Answer 6

K+ out on the basolateral side of a principal cell

Question 7

What does AQP3 and AQP4 transport?

Answer 7

H2O out on the basolateral side of a principal cell

Question 8

Give some examples of diseases of the principal cell of the collecting duct

Answer 8

Diabetes insipidus - AQP2
Liddle’s syndrome - ENaC
Pseudohypoaldosteronism

Question 9

Give an example of a potassium-sparing diuretic

Answer 9

Amiloride

Question 10

What does amiloride do?

Answer 10

Blocks ENaC inhibiting Na+ uptake at late distal tubule which reduces K+ secretion

Question 11

What is secreted and reabsorbed in α intercalated cells of the collecting duct?

Answer 11

H+ secretion and HCO3^- reabsoprtion

Question 12

Membrane proteins/channels of α intercalated cell

Answer 12

Apical
- H+ out using ATP

Basolateral

• AE1 - Cl^- in and HCO3^- out
• Chloride ion channel - Cl^- out

Question 13

What is AE1?

Answer 13

An anion-exchanger

Transports HCO3^- out and Cl^- in

Question 14

What do mutations in AE1 cause?

Answer 14

Distal renal tubular acidosis

• genetic inheritance
• nephrocalcinosis
• metabolic acidosis
• nephrolithiasis

Question 15

What occurs when a gain-of-function mutation in AE1 occurs in an α intercalated cell?

Answer 15

It forms AE1 on the apical side too –> acidosis

Question 16

Membrane proteins/channels of ß intercalated cell

Answer 16

Apical
- AE - HCO3^- out and Cl^- in

Basolateral

• H+ out using ATP
• Chloride ion channel - Cl^- out

Question 17

Permeabilities of medullary collecting duct

Answer 17

• Low Na+ permeability

- High H2O and urea permeability in the presence of vasopressin

Question 18

Where is H+ secreted and reabsorbed?

Answer 18

Secretion: Proximal tubule, principal cell and α intercalated cell
Reabsorption: ß intercalated cell

Question 19

Where is HCO3^- secreted and reabsorbed?

Answer 19

Secretion: ß intercalated cell
Reabsorption: proximal tubule, principal cell and α intercalated cell

Question 20

Where does aldosterone act?

Answer 20

Principal cells in collecting duct system

Question 21

What do principal cell types reabsorb and secrete?

Answer 21

Na+ and H2O reabsorption

K+ and H+ secretion

Question 22

What do intercalated cell types reabsorb and secrete?

Answer 22

H+ secretion/reabsorption

HCO3^- reabsorption/secretion

Question 23

What types of intercalated cells are there? What does their ratio depend on?

Answer 23

α and ß

Depends on the acid-base state of the body

Question 24

What membrane channels are found on the apical side of a principal cell of distal tubule?

Answer 24

• ENaC
• ROMK
• Aquaporin 2

Question 25

What is the role of ENaC?

Answer 25

Transport sodium ions into the cell on the apical side of the principal cell of the distal tubule

Question 26

What is the role of ROMK in the principal cell of the distal tubule?

Answer 26

Transport K+ out