tompat
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why creatinine(389)  is not taken for renal plasma flow but for GFR?
I MEAN IT'S EXCRETION is similar to PAH, THEN WHY NOT renal Plasma flow but GFR?
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| po
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for MEASURING GFR you need something that is filtered entirely but not secreted or reabsorbed so that amout filtered should be equal to amount of substance---ideally inulin is best candidate.But creatinine serves purpose[approximately], though it is secreted it negligible amount.
for MEASURING RPF we need to understand-RPF will be greater than GFR otherwise what's the purpose of kidneys?
so to measure RPF,we need something filtered and secreted entirely so that the extraction ratio is high,like it should reflect the amount of renal plsma that is going to go thru the filtration rather than the filtered as in GFR.PAH serves this purpose by virtue of its some other required points those are it is not metabolised /stored/produced by kidney/doesnot itself affect the RBF.
RPF term is used since kidney filters plasma,& amount of RBCS remain same.
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| d
Forum Newbie
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 Your answer confused me more.
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| po
Forum Elite
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that was the best I cud do,hope some one else would give the valuable 2nd opinion
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| new_n_lost
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Agree with Po
To Measure GFR we use a substance which is generally free-filtered while neither being reabsorbed nor secreted Creatinine is the only substance in the body which does that therefore it is considered to be the best Index for GFR. The Line Drawn for Creatinine is a bit higher than Inulin cos Creatinine is also secreted in minute amounts.
To Measure RBF WE a Substance which is mostly secreted and that is PAH.
I essentially have said the same thing as Po. And still if someone cant understand the reasons then they surely have to go thru the Concepts of Renal Physiology.
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| mytime
Kick my butt!
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I agree too. Good q though, TOMPAT!
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| tompat
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oops i have made a huge mistake here, i hate myself!
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| new_n_lost
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tompat wrote:oops i have made a huge mistake here, i hate myself!
R u Being Sarcastic or U really did make a Mistake ???
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| d
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 This is good and Thanks!
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| tompat
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to nnl:
i was never and will never be sarcastic on this forum.
i did make a mistake by saying that creatinine's excretion is similar to PAH while in fact isn't!!
while PAH is excreted completely,whatever goes in nephron and peritubular capillaries, creatinine is not.
creatinine isn't completely secreted!!
and as u guys said very small amount of creatinine is secreted it has to be taken for GFR.
well just to mention here any substance which is freely filtered thru glomerulus,only 20% of it will be filtered and 80% shall remain in peritubular capillaries during it's passage thru kidney.
note the correlation,GFR IS 120ml/min and RPF is 600ml/min, that is GFR is 20%of RPF.(hey is there any anxiety defense mechanism i m using here?)
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| po
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renal physio is tricky topic
thanks nnl,I think I can skip this topic probably no got to revise however confident I feel about it.
Goodluck
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| new_n_lost
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Tompat ............. By that I meant U made a huge mistake by asking an easy question 
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| bioguy
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no doubt this was (and is) the weakest topic for me, then and now
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