Question about Aldosterone

[MedGrl@2022]

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Why does aldosterone cause secretion of K+ and H+ if its purpose is to increase the amount of water that is retained by the body? Wouldn't the secretion of K+ and H+ ions cause more H2O to "follow the osmotic gradient" be secreted with these ions?

Thank you,

Verónica

 

[Leonardo Noto]

Two things, Veronica. First, the general consensus now is that aldosterone's most important role in the body is in potassium homeostasis. But to answer your question, aldosterone causes sodium retention and potassium secretion primarily by upregulating the sodium-potassium ATPase pump in the cortical collecting tubule of the distal nephrons -- for every 3 Na ions that are reabsorbed, 2 K ions are secreted. This is not an electrically neutral proposition and it requires energy in the form of ATP, hence the name Na-K ATPase pump (many refer to it as "Na-K pump" in undergrad but "ATPase" should really be added to the name because ATP powers the pump).

Dr. Leonardo Noto
www.leonardonoto.com or follow me on Twitter @DrLeonardoNoto

 

[YouNeverKnow22]

Why does aldosterone cause secretion of K+ and H+ if its purpose is to increase the amount of water that is retained by the body? Wouldn't the secretion of K+ and H+ ions cause more H2O to "follow the osmotic gradient" be secreted with these ions?

Thank you,

Verónica

Don't over think it here...the main function of Aldosterone is to act on the DCT by increasing Na+ uptake, as a secondary consequence H20 gets reabsorbed. This action also causes K+ to be secreted with H+. Also remember we are dealing with homeostasis so be able to reason what would happen to BP as well.


Good luck.

 

[MedPR]

Why does aldosterone cause secretion of K+ and H+ if its purpose is to increase the amount of water that is retained by the body? Wouldn't the secretion of K+ and H+ ions cause more H2O to "follow the osmotic gradient" be secreted with these ions?

Thank you,

Verónica

H2O follows Na+. If K+ goes one way (secreted), Na+ goes the other way (reabsorbed) and H2O goes with it.