USMLE Forums - View Single Post - Effects of Angiotensin II on GFR, RPF, and FF
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Old 09-09-2011
alaahoda2001 alaahoda2001 is offline
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Originally Posted by bebix View Post
Just think in numbers here:

If Q = RPF = 600 ml/min

Normal FF = 20% ==> GFR 120 / RPF 600

Vc (AA or EA) will decrease Q = new Q 400 (doesn't matter really the number here)

Since AII Vc EA >>>AA = Hydrostatic pressure between both arterioles will also increase => GFR increases (because this number depends on the hydrostatic and oncotic pressure, and since HP goes up => more filtration)

net outcome => FF > 20%

Remember, FF is a percentage of RPF and not an absolute even if the GFR stays the same, since the denominator decreases, the percentage must increase!

good luck!

For more info, check here:
Concepts in medical physiology
Well said Bibex,
i actually tend to say that answer D and that was my answr before i read the kaplan text and videos of 2010
please watch the video in the link below and tell me if you can explain it
i really want to know what do you think?

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