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 does anyone understand why  



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Author9 Posts
  #1

drinking large amounts of water would not affect gfr? wouldn't the decreased oncotic pressure in the capillaries favor an increase in gfr?




  #2

ok, this is not a documented answer, it's just my idea about this issue, the way I understand it....
water is a hypotonic fluid, so it won't stay long in your blood vessels, it'll go into the interstitial compartment. so the increase in hydrostatic pressure or decrease in oncotic pressure in the kidney won't be significant enough as to modify your GFR. the effect it has though on your diuresis is due to the negative feedback on ADH release, which will increase your free water output. you ingest hypotonic, you lose hypotonic.
waiting for other opinions.....


  #3

i agree with AlinaT, we should keep in mind that main factor determinig gfr is vascular hydrostatic pressure, and that wont be affected to a great extent due to the reason given by Aline T.
i too will wait for otehr opinions if any.


  #4

Hmm.-Always thought water was isotonic.


  #5

great thinking mjl1717, would u eloborate a bit on this?


  #6

if water is isotonic.....then why does it get to dilutional hyponatremia in psychogenic polydipsia or when a patient drinks water after any loss of fluid? this is how I deducted the idea of hypotonicity of water...
what do u think, mjl?


  #7

water is hypotonic, i believe. alina, i like your answer.


  #8

check this out:

http://www2.kumc.edu/ki/physiology/course/seven/7_3.htm


  #9

thank you for ur kind appreciation, bluedusk, and thank you dxtxpx for the site. i guess now my ans is documented....? smiling face





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