A researcher wants to measure the true glomerular filtration rate in an experimental animal. Which substance's clearance most closely approximates the actual GFR?
- A Inulin ✓
- B Creatinine
- C Para-aminohippuric acid
- D Glucose
Correct answer: A. Inulin
Explanation
Inulin is freely filtered at the glomerulus and is neither reabsorbed nor secreted by the tubule, so its clearance equals the actual GFR. Creatinine clearance slightly overestimates GFR because creatinine undergoes modest tubular secretion. PAH is both filtered and avidly secreted, so its clearance approximates renal plasma flow, not GFR. Glucose is completely reabsorbed below its transport maximum, giving a clearance of essentially zero.
Reference: Ganong's Review of Medical Physiology, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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