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  #1  
Old 04-02-2013
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Kidney Effects of angiotensin II

Concept problem:
Direct quote from kaplan physiology renal section:
"Because angiotensin constricts the efferent more than the after end arterioles,it tends to preserve glomerular capillary pressure as renal resistance increases and plasma flow decreases.
Thus GFR may show Bly minimal decrease under these condition."

Question
As I know,when efferent arterioles constricts ( radius to the 4th power decrease), glomerular capillaries pressure increases,and thus GFR should increase...

Why it decrease as stated in the text?pls guide..
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Old 04-02-2013
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I had to revise my notes to get an answer.. Here's what i found:
Yes you are right, effects of efferent VC is:
*decrease RPF > increased FF
* increased pressure ( hydrostatic pressure) > increased GFR

The decrease in RPF and increased FF leaves behind unfiltrable solutes ( i think of it as the plasma moving slowly so all the filtrable solutes get out leaving insoluble ones in the capillary) .. Those insoluble solutes create an oncotic pressure that opposes filtration > decrease GFR (think: slow RPF gives time to those insoluble solutes to exert an apposing pressure).
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Old 04-03-2013
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Sorry, due to typo error, I need to correct some of the words to prevent confusion.

Direct quote from kaplan physiology renal section:
"Because angiotensin constricts the efferent more than the afferent arterioles,it tends to preserve glomerular capillary pressure as renal resistance increases and plasma flow decreases.
Thus GFR may show Only minimal decrease under these condition."

Question
As I know,when EFFERENT arterioles constricts ( radius to the 4th power decrease), glomerular capillaries pressure increases,and thus GFR should increase. It means it can filtrate more fluid and dissolved substances per minute In proximal tubules.

But in kaplan lecture videos,It is contradictory to what I understood?pls guide..
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Old 04-03-2013
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Quote:
Originally Posted by ` Faith ` View Post
I had to revise my notes to get an answer.. Here's what i found:
Yes you are right, effects of efferent VC is:
*decrease RPF > increased FF
* increased pressure ( hydrostatic pressure) > increased GFR

The decrease in RPF and increased FF leaves behind unfiltrable solutes ( i think of it as the plasma moving slowly so all the filtrable solutes get out leaving insoluble ones in the capillary) .. Those insoluble solutes create an oncotic pressure that opposes filtration > decrease GFR (think: slow RPF gives time to those insoluble solutes to exert an apposing pressure).
I got what u meant.
but then why in kaplan stated "GFR shows only minimal decrease under these conditions( ANGIOTENSIN II action)?"
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Old 04-03-2013
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What I know that angiotensin 2 increases the GFR!
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Old 04-03-2013
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Angiotensin II constricts efferent arterioles leading to inceased GFR and dec RPF, so FF also inc.
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Old 04-03-2013
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Also have a look at this thread, it is discussed in detail.

Effects of Angiotensin II on GFR, RPF, and FF
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Old 04-03-2013
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Quote:
Originally Posted by mutant View Post
Also have a look at this thread, it is discussed in detail.

Effects of Angiotensin II on GFR, RPF, and FF
I have read the discussion there...but there is not one final conclusion.
Kaplan said it differently...
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