MEDizzy - The following information was obtained in a 20-year-old

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RENAL & ACID-BASE PHYSIOLOGY

The following information was obtained in a 20-year-old college student who was participating in a research study in the Clinical Research Unit: PLASMA: [Inulin] = 1mg/mL, [X] = 2 mg/mL URINE: [Inulin] = 150 mg/mL,[X] = 100 mg/mL, Urine flow rate = 1 mL/min Assuming that X is freely filtered, which of the following statements is most correct?

ExplanationTo answer this question, calculate the glomerular filtration rate (GFR) and CX. GFR = 150 mg/mL × 1 mL/min ÷ 1 mg/mL = 150 mL/min. CX = 100 mg/mL × 1 mL/min ÷ 2 mg/mL = 50 mL/min. Because the clearance of X is less than the clearance of inulin (or GFR), net reabsorption of X must have occurred. Clearance data alone cannot determine whether there has also been secretion of X. Because GFR cannot be measured with a substance that is reabsorbed, X would not be suitable.