Sketchy Pharm: K+ Sparing Diuretics Flashcards
Which cells handle the sodium absorption in the collecting duct?
The principal cells (just like how this scene takes place in the Principal Court)
Just like in all other sections of the nephron, sodium in the collecting duct is absorbed through the basolateral membrane by ______________.
a sodium/potassium exchanger (like the mom taking her kid’s peanuts and giving him a banana)
How is sodium absorbed through the apical membrane of the collecting duct?
Sodium is absorbed through the ENaC proteins (Epithelial Na Channels) in the apical membrane. These channels are inducible by aldosterone.
(Think of the salt-E sNaCk cart that is passing peanuts to the kid in the space that represents the intracellular compartment.)
Why is potassium excreted in the collecting duct?
Recall that in the other parts of the nephron electrolytes were exchanged to maintain membrane charge. Here, however, sodium is absorbed alone. This creates a negative luminal charge that pulls potassium into the filtrate.
(Think of the salt-E sNaCk cart hitting the banana stand and causing bananas to spill into the gutter.)
Which cells secrete H+ into the lumen?
Alpha-intercalated cells (like the alpha-intercontinental food truck pumping acid into the gutter)
True or false: H+ is passed into the filtrate passively.
False. It is pumped in with an ATPase (like the three P batteries on the food truck).
Which channels does aldosterone activate?
- ENaC
- Potassium channel
- Basolateral Na/K exchanger
- H+ pump
(Think of the Mineral Court manager’s keys in the peanut cart, the banana stand, the acid truck, and the vending machine.)
Which diuretics block ENaC?
Triamterene and amiloride
(These are represented by the parents who are furious at the salty options and are tipping the salt-E sNaCk cart into the gutter. They are offering healthier options: TangERINEs and AlMOnDs.)
Why do ENaC antagonists prevent potassium excretion?
Potassium excretion happens because of the negative luminal charge generated by sodium absorption through the ENaC proteins. Without those, potassium is not excreted.
Which two drugs inhibit aldosterone?
Eplerenone and spironolactone (like the teacher with the apPLE and the health inspector’s SPIRal-bound notebook)
Aldosterone antagonists are especially useful in the treatment of __________________.
Conn syndrome (hyperaldosteronism)
Think of the tall mineral mountain behind the potassium-sparing diuretics.
Why are aldosterone antagonists useful in the treatment of CHF?
In CHF, the RAAS pathway is overactivated because of decreased renal perfusion. As such, aldosterone levels will be high. Aldosterone antagonists can cause diuresis –improving the symptoms of CHF – directly at the last common pathway of the RAAS.
(Think of the little girl dressed as an angel with the floppy heart balloon –she represents how spironolactone and eplerenone have been shown to improve mortality in CHF.)
Secondly, high levels of aldosterone have a negative effect on the remodeling of the heart. Thus, antagonizing it prevents this deleterious remodeling.
(The angel girl is also next to a mineral mountain being remodeled.)
How does amiloride help treat nephrogenic diabetes insipidus?
In addition to preventing sodium entry into principal cells, amiloride also blocks lithium entry.
(Think of the peeing fountain in the distance behind amiloride.)
Triamterene can be used to treat what genetic disorder?
Liddle syndrome (constitutional overactivation of ENaC channels)
(I have no idea why this is the symbol, but Sketchy has a LIttLE gnome falling into the gutter next to amiloride and triamterene.)
What side effects are associated with the potassium-sparing diuretics?
- Hyperkalemia – kind of obvious (think of the celebrating banana saleswoman)
- Non-anion gap metabolic acidosis (think of the acid truck pulling away from the threatening, health-conscious parents and spilling acid into the cell compartment)
Taken together, these represent type 4 renal tubular acidosis (the four test tubes making up the letter K).
