Distal Tubule and Collecting Duct Genes Flashcards
What are the 2 cell types of the distal tubule?
- Principal
- Intercalated
What are the two types of collecting duct cell types?
Principal and intercalated
What are the two types of intercalated cell?
α and ß
α is acid-releasing and more present in Western, high-protein, diets
What membrane channels are found on the basolateral side of a principal cell of the collecting?
Kir 2.3
AQP3
AQP4
What membrane channels are found on the apical side of a principal cell of the collecting?
ENaC
ROMK
Aquaporin 2
What does Kir2.3 transport?
K+ out on the basolateral side of a principal cell
What does AQP3 and AQP4 transport?
H2O out on the basolateral side of a principal cell
Give some examples of diseases of the principal cell of the collecting duct
Diabetes insipidus - AQP2
Liddle’s syndrome - ENaC
Pseudohypoaldosteronism
Give an example of a potassium-sparing diuretic
Amiloride
What does amiloride do?
Blocks ENaC inhibiting Na+ uptake at late distal tubule which reduces K+ secretion
What is secreted and reabsorbed in α intercalated cells of the collecting duct?
H+ secretion and HCO3^- reabsoprtion
Membrane proteins/channels of α intercalated cell
Apical
- H+ out using ATP
Basolateral
- AE1 - Cl^- in and HCO3^- out
- Chloride ion channel - Cl^- out
What is AE1?
An anion-exchanger
Transports HCO3^- out and Cl^- in
What do mutations in AE1 cause?
Distal renal tubular acidosis
- genetic inheritance
- nephrocalcinosis
- metabolic acidosis
- nephrolithiasis
What occurs when a gain-of-function mutation in AE1 occurs in an α intercalated cell?
It forms AE1 on the apical side too –> acidosis
Membrane proteins/channels of ß intercalated cell
Apical
- AE - HCO3^- out and Cl^- in
Basolateral
- H+ out using ATP
- Chloride ion channel - Cl^- out
Permeabilities of medullary collecting duct
- Low Na+ permeability
- High H2O and urea permeability in the presence of vasopressin
Where is H+ secreted and reabsorbed?
Secretion: Proximal tubule, principal cell and α intercalated cell
Reabsorption: ß intercalated cell
Where is HCO3^- secreted and reabsorbed?
Secretion: ß intercalated cell
Reabsorption: proximal tubule, principal cell and α intercalated cell
Where does aldosterone act?
Principal cells in collecting duct system
What do principal cell types reabsorb and secrete?
Na+ and H2O reabsorption
K+ and H+ secretion
What do intercalated cell types reabsorb and secrete?
H+ secretion/reabsorption
HCO3^- reabsorption/secretion
What types of intercalated cells are there? What does their ratio depend on?
α and ß
Depends on the acid-base state of the body
What membrane channels are found on the apical side of a principal cell of distal tubule?
- ENaC
- ROMK
- Aquaporin 2
What is the role of ENaC?
Transport sodium ions into the cell on the apical side of the principal cell of the distal tubule
What is the role of ROMK in the principal cell of the distal tubule?
Transport K+ out
