Inulin clearance is equal to
I. Substances used to measure GFR:
The substance should be —
→neither reabsorbed nor secreted
→not metabolized by the body.
a. Inulin: polymer of fructose, meets above these criteria in human and most animals and is extensively used to measure GFR
CINULIN= UINULIN X V
b. 51Cr-EDTAis also used but inulin remains the standared substance. Q
c. Endogenous creatinine clearance is easy to measure (GFR) and is worth while index of renal function
d. NMS/319 →other substances used to measure GFR are →mannitol sorbitol, sucrose (I.V.), isothalamate, radioactive cobalt labelledvit. B12, radioiodine — labelledHypaque.
II. Effective RPF = 625 ml/min. = PAH clearance