Which of the following product is primarily filtered with little secretion or reabsorption in renal tubules?: (A) Sodium, (B) Inulin, (C) Glucose, (D) Amino acids
Answer is B. In addition to the requirement that it be freely filtered and neither reabsorbed nor secreted in the tubules, a substance suitable for measuring the GFR should be nontoxic and not metabolized by the body. Inulin, a polymer of fructose with a molecular weight of 5200 that is found in Jerusalem aichokes (Helianthus tuberosus), meets these criteria in humans and most animals and is extensively used to measure GFR.Ref: Ganong's review of Medical Physiology, 23rd edition, Page no: 645