scorpio
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The clearance of several substances was measured at a constant glomerular filtration rate and constant urine flow rate, but at increasing plasma concentrations of the substance. Under these conditions, clearance will increase at high plasma concentrations for which of the following substances?
A.Creatinine
B.Mannitol
C.Penicillin
D.Phosphate
E.Urea
Pls explain. Thanks
-Scorpio.
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| Geroo
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phosphate?because it follows transport maximum reabsorption.I'm not sure
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| sturge_weber
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creatinine
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| Geroo
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but if GFR is kept constant creatinine clearance won't change with change in plasma conc.creatinine clearance=GFR.
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| sturge_weber
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what i think here is , that creatinine is both freely filtered and also secreeted in the urine, but the amount being filtered is very less, hence we take creatinine clearance equal to gfr, but when we keep on increasing the plasma concentrations of creatinine, the secreted amount will increase and hence gfr will also increase
well i dont know if thats the ans, but thats what i think
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| gogetit
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y not penicillin?
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| Geroo
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penicillin is secreted with T-max.that means when the plasma coc increases receptors become saturated and less will be secreted so clrearance will decrease.same like(PAH).hope I'm right
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| gogetit
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thanks geroo
now think the answer is D -phosphate
For a substance to get an increase in clearance when its plasma concetration increases..it should behave like Glucose (other similar ones ..Ca, sulphate, phosphate etc..)
Mannitol, Sucrose, Innulin (freely filtered ones)--Clearance = GFR (independent of Plasma Conc.)
Penicillin is like PAH at low plasma level its clearance increase but decrease in higher Conc..(carrier saturation) the filtered load increase but so does the part of to be secreted but it will be too much to be secrted in a single pass so likely to appear in plasma again
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| scorpio
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Dear friends,
Although I don't have the documented right answear but now I am pretty much sure the right answear is "D.Phosphate"- Dr gogetit has nicely explained the reason.
Ref:
1.Kap. Phys. fig.Vll-2-1, page#320
2.Kap. Phys. Review Q no-17, page#341 (exlanation on page#346)
Thanks you friends for your valuable time.I hope the same again.
Good luck.
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| sturge_weber
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well its a physio q bank q, and the ans is phosphate, and i got it wrong there too, and the same mistake here too
well explained gogetit
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