aldosterone and vasopressin

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theonlytycrane

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Do each of these hormones affect both the distal tubule and collecting duct in the nephron? I was initially under the impression that aldosterone helped to retain sodium in the distal tubule and that vasopressin helped to retain water in the collecting duct. However, a few sources that I'm reading from seem to imply that each hormone has important effects in both places.

Thanks!

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Yes, aldosterone and vasopressin (ADH) play a role in both distal convoluted tubule and collecting duct. The key here is to understand what each hormone does:

Aldosterone --> sodium reabsorption. So you would expect some sodium channels or Na+/K+ ATPases (reabsorbing sodium; excreting potassium) in these regions

ADH --> water reabsorption. So you would expect water channels/aquaporins involved

Because both aldosterone and ADH are involved in regulating plasma osmolarity and blood volume, it's reasonable to expect them to have a much wider influence in renal physiology rather than simply being localized into specific regions.

Aldosterone commonly acts in the distal tubule, but it does serve a role in the collecting duct. The collecting duct has sodium channels and Na+/K+ ATPases, which increase in production via aldosterone stimulation. For ADH, the arginine vasopressin receptor 2 is found in the distal convoluted tubule.

Interestingly, ADH also has a role in influencing electrolyte transport by stimulating the Na+/K+/2Cl- cotransporter (which reabsorbs sodium, potassium and chloride ions) in the ascending limb of loop of Henle. But that's just some extra stuff I found by searching more about the functions of the hormone.

So while aldosterone and ADH primarily act on the distal tubule and collecting duct respectively, they aren't necessarily restricted in these regions. These hormones can act on other regions while maintaining similar regulatory functions.

Also, this chart, while rather complex, can help visualize the renal physiology and regulation involved.

2000px-Kidney_nephron_molar_transport_diagram.svg.png
 
Great explanation, just be careful with that infographic as it contains way more information (drug targets, other renal relevant hormones/neurotransmitters than the MCAT would not expect you to know. You will learn it in med school though! Good luck.
 
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