[ICUdoc]

BRS Physiology states.......

" In the absence of ADH, the principal cells are virtually impermeable
to water"

What????

Aldosterone still causes Na+ and water reabsorption in the Principal cells doesn't it???

 

[adrenaline106]

Aldosterone doesn't increase water permeability directly... It increases Na reabsorption and water follows... ADH inserts aquaporins through v2 receptors on collecting ducts increasing water permeability only... Also there are v1 receptors on blood vessels which vasoconstriction in presence of ADH.. I think this is how it works..

BRS Physiology states.......

" In the absence of ADH, the principal cells are virtually impermeable
to water"

What????

Aldosterone still causes Na+ and water reabsorption in the Principal cells doesn't it???

 

[coliris]

Aldosterone doesn't increase water permeability directly... It increases Na reabsorption and water follows... ADH inserts aquaporins through v2 receptors on collecting ducts increasing water permeability only... Also there are v1 receptors on blood vessels which vasoconstriction in presence of ADH.. I think this is how it works..

Yep, I agree. Water may follow Na reabsorption with Ald, but it's not as significant as with ADH.

 

[deutsch_schi]

I have the same question. If water can diffuse thru principal cells or the interstitial tissue following Na flow with Aldosterone, how can the hyperosmolarity maintain?? The impermeability of water of the initial step to form the inner medullary hyperosmolarity, right??