Diuretics: Ch.2-4: Potassium sparing drugs Flashcards
What is a principal cell?
the site of Na/K/H2O transport in the collecting duct
About how much NaCl is reabsorbed in the collecting duct?
5-10%
What is the function of the alpha-intercalated cell of the collecting duct?
it’s the major site of H+ secretion
What channel is responsible for Na+ reabsorption in the collecting duct?
ENaC (epithelial Na+ channels)
This is a K+-sparing diuretic that is a competitive aldosterone receptor antagonist in the collecting duct.
- eplerenone
- spironolactone
What is eplerenone? How does it work? What is it used to treat?
- a K+-sparing diuretic
- a competitive aldosterone receptor antagonist (specific)
- tx for:
- hyperaldosteronism
- K+ depletion
- HF
Dx?
- overactive ENaC –> increased Na+ resorption in the collecting tubules –> hypokalemia, metabolic alkalosis, and HTN but low aldosterone
Liddle Syndrome
What are the SEs of amiloride and triamterene?
hyperkalemia –> arrhythmias
Why is spironolactone anti-androgenic?
- it prevents testosterone synthesis by blocking 17-alpha-hydroxylase
- blocks the androgen receptor
Aldosterone works at the _____ of the nephron, promoting Na+ reabsorption and water retention.
collecting duct
Which part of the nephron is most important for K+ regulation?
the collecting duct
This is the site of Na/K/H2O transport in the collecting duct.
the principal cells
What is the major site of H+ secretion in the collecting duct?
the alpha-intercalated cell
Aldosterone binds to _____ receptors.
intracellular
______ works at the collecting duct, promoting Na+ reabsorption and water retention.
Aldosterone
Aldosterone increased gene transcription to cause ____.
increased # of channels in the collecting duct
What causes Liddle Syndrome?
it’s an auto dominant gain of function mutation
What is the tx for Liddle Syndrome?
- amiloride
- triamterene
Where does aldosterone exert its action?
the collecting duct
What is Liddle Syndrome?
overactive ENaC –> increased Na+ resorption in the collecting tubules –> hypokalemia, metabolic alkalosis, and HTN but low aldosterone
What is the main job of a K+-sparing diuretic?
- to antagonize the effects of aldosterone or ENaC
What are the SEs of spironolactone?
- normal anion gap metabolic acidosis
- gynecomastia
- anti-androgen
- impotence
- decreased libido
Why do spironolactone and eplerenone reduce morbidity and improve mortality in HF patients?
they reduce myocardial remodeling induced by high levels of aldosterone
What is spironolactone? How does it work? What is it used to treat?
- a K+-sparing diuretic
- a competitive aldosterone receptor antagonist (nonspecific)
- tx for:
- ascites
- hyperaldosteronism
- K+ depletion
- HF
- PCOS
The potassium-sparing diuretics act upon the _____.
collecting duct
Aldosterone works at the collecting duct, promoting ____ reabsorption and _____ retention.
Na+; water
This is a K+-sparing diuretic that blocks Na+ reabsorption thru ENaC and is a tx for Liddle Syndrome and nephrogenic DI.
amiloride
What are the potassium sparing diuretics?
thiazides
What is triamterene? How does it work? What is it used to treat?
- a K+-sparing diuretic
- blocks Na+ reabsorption thru ENaC
- tx for:
- Liddle Syndrome
- hyperaldosteronism
- K+ depletion
- HF
In a normal kidney, why is so much K+ wasted at the collecting duct?
because Na+ is resorbed and NOT exchanged (ENaC)
What is amiloride? How does it work? What is it used to treat?
- a K+-sparing diuretic
- blocks Na+ reabsorption thru ENaC
- tx fo:
- Liddle Syndrome
- nephrogenic DI (from lithium)
- hyperaldosteronism
- K+ depletion
- HF
