Which of the following (Ideal) substance used to measure GFR

(Inulin) (265-66-K.S 3rd) (706,7J2-GN) (645- Ganong 23rd)(1) Measurement of GFR - A substance that is completely filtered but neither reabsorbed nor secreted should be used to measure GFR. Inulin is a substance that is completely filtered, but it is neither reabsorbed nor secreted. So Inulin is the ideal substance used to measure GFR.* Creatinine clearance is also used to measure GFR, are inaccurate at low creatinine levels.* *Endogenous creatinine clearance is a worthwhile index of renal functions(2) Measurement of Renal plasma flow. To measure renal plasma flow, a substance, which is filtered and secreted but not reabsorbed should be used. Such a substance is Para-aminohippuric acid (PAH). PAH clearance indicates the amount of plasma passed through kidneys.* Diodrast clearance also can be used to measure renal plasma flow.(3) Measurement of Renal blood flow. Two factors1. Renal plasma flow - PAH clearance2. Percentage of plasma volume in the bloodRenal blood flow =Renal plasma flow% of plasma in blood