Venkatesh weighs 157 lbs, and you have just injected him intravenously with a mi
ID: 177502 • Letter: V
Question
Venkatesh weighs 157 lbs, and you have just injected him intravenously with a mixture of^14C-inulin and sucrose. After two hours the plasma concentration of inulin was 0.80 mg/ml and sucrose was 1.2 mg/ml. Measurements of the urine showed the concentrations of inulin and sucrose to be 80 mg/l and 60 mg/ml respectively. Urine production (both kidneys) was 1.25 ml/min. (a) What was the Venkatesh's glomerular filtration rate? (b) What was the clearance rate for sucrose? (c) How would you account for the clearance rate for sucrose? Given what you know about sucrose, which explanation is more likely? SHOW YOUR WORK !Explanation / Answer
To calculate Glomerular Filtration Rate (GFR) we use the formula
(Concentration of solutes in Urine x urine flow) / Plasma concentration for all solutes =
Concentration of Urine = (80 x10-3 mg/ml +60mg /ml) = 0.08+60 =60.08 mg/ml
Urine flow = 1.25 ml/min
Plasma concentration =(0.8+1.2) =2 mg/ml
GFR = (60.08)/2 = 30.04 ml/min
Renal clearance of sucrose=
V = solute in urine = 60mg/ml
U = flow of urine = 1.25 ml/min
[p]= solute concentration in plasma = 1.2 mg/ml
C = 60x 1.25/1.2 =75 ml/min
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