Aldosterone and ADH

[663697]

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On the Bio1 Qpack #80, it says that water is passively reabsorbed after aldosterone causes Na+ to be reabsorbed into the blood. In other sources, I've also seen that ADH gets released to insert aquaporins into the tubules so that water is reabsorbed down the gradient. Are these separate events or is the latter just a more detailed way of explaining the osmosis that occurs?

 

[rabbott1971]

I believe those are separate processes that both happen in the kidney. Aldosterone creates an osmotic gradient affecting water reabsorption, and ADH (anti-diuretic hormone) literally creates water channels for reabsorption.

You probably got it right, but the way I thought about this question was, if aldosterone is lowered, Na+ reabsorption goes down, Na+ excretion goes up, now we have blood that's lacking salt, so we certainly won't want to water it down more. In fact it needs to be concentrated to maintain functional levels of ions. So volume will go down, and pressure will follow. That was my impression anyway, smarter people might have a better explanation. Question and solution attached.