Ideal substance for measuring GFR should have all characteristics except
Should be secreted in tubules
Should be non-toxic
Should not remain in the body
Should not be protein bound
The Ideal substance to measure GFR is Inulin or following reasons ; It is non-toxic; It is freely filterable by the glomeruli; it is not bound to proteins It is neither secreted nor reabsorbed by the tubules; It is not synthesized, stored, or destroyed by the kidney . Thus, Filtered inulin = excreted inulin .Hence, it will give an exact estimate of the GFR. Endogenous creatinine clearance is used most commonly used to estimate the GFR.
Excretory System (Kidney, Bladder) Acid-Base Balance