Nephron 3 Flashcards
What are cells found within the collecting duct?
Principal cells- alpha and beta
Intercalated cells
Identify the key permeability properties of principal cells in collecting duct
Na and H2O reabsorption
K+ and H+ secretion
Identify the key permeability properties of alpha and beta intercalated cells
Alpha- H+ secretion and HCO3- reabsorption
Beta- H+ reabsorption and HCO3- secretion
Describe the molecular basis of transport in the late distal and cortical collecting duct
Sodium ATPase is the driving force
K+ channel maintains negative membrane potential
ENaC allows Na to move across the apical membrane and leaves through the basolateral membrane (net reabsorption of Na)
ROMK is a potassium channel that allows the movement of K+ out of the apical membrane
Aquaporin 2 allows the movement of H2O across the apical membrane while AQP3 and AQP4 remove H2O through the basolateral membrane
Why would the number of alpha or beta intercalated cells change?
This changes in response to the acid base status of the body. For example if you need to retain more hydrogen ions, you will have more alpha IC cells
What is amiloride?
It is a diuretic that promotes urine loss by BLOCKING ENaC
By blocking ENaC in the principal cell, Na reabsorption is prevented which inhibits water reabsorption leading to more urine loss
What is diabetes insipidus disease?
An inherited disease that leads you to urinate too much
What is Liddle’s syndrome and what causes it?
Liddle’s syndrome is an inherited disease that is caused by mutations in ENaC channels
What are the symptoms of Liddle’s syndrome
Too much Na retention
Absorbing too much Na means more water retention and so expansion in ECFV
This means HYPERTENSION (high bp)
Hypokalaemia (low plasma potassium)
Metabolic alkalosis (pH s higher than normal)
What are the 3 subunits that make up ENaC?
Alpha
Beta
Gamma
What can increased ECFV and cardiac output lead to?
Hypertension
