Step I ADH help

[MissMedicine]

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Does ADH work at the cortico or medullary CD? First Aid draws it in the medullary but I thought I read somewhere that it works in the distal tubule and corticocollecting duct.... maybe im thinking of aldosterone..

thanks for your help

 

[mpsheeha]

It is my understanding that ADH has it's osmotic effects at both (the cortical and medullary collecting ducts). If you want to get specific there are V2 receptors in the distal convoluted tubule and the collecting ducts through which ADH elicits aquaporin insertion. I think the reason you often see only the medullary collecting duct listed is that this is the major site where urine concentration occurs and water is brought back through the aquaporins. The kidney has an osmotic gradient ("counter current gradient") that goes from about 300-1200 mOsmolar.......increasing as you move into the medullary. This is essentially the osmotic pull on the water inside the kidney tubules. Thus, when ADH induces the insertion of aquaporins, the greatest pull on the water is in the medulla.

Hope this helps some and good luck studying.

 

[Idiopathic]

Does ADH work at the cortico or medullary CD? First Aid draws it in the medullary but I thought I read somewhere that it works in the distal tubule and corticocollecting duct.... maybe im thinking of aldosterone..

thanks for your help

That is the description of aldosterone. Just think of ADH acting at the colecting duct (as well as some vascular pressor effect).

 

[jed2023]

Every textbook I've read says that ADH has an effect at the late distal tubule (but not early distal tubule), in addition to its well known effect at the collecting duct. Even good ole' Costanzo says this. If you are forced to choose between collecting duct and distal tubule, though, it's a better bet to pick collecting duct.

 

[Idiopathic]

After some Googling, I see that you are 100% right. ADH has effects at both locations, just like aldosterone.