Inulin is used as an indicator of glomerular filtration rate (GFR or 'F') because it is freely filtered and not reabsorbed. The GFR has been calculated to be 150 ml/min. Plasma inulin concentration is 1mg/ml; plasma glucose is 1mg/ml; urine output is 60 ml/min. The glucose excretion rate is 0mg/min. a) What is the urinary inulin concentration? b) What is the inulin excretion rate? c) Determine glucose clearance and the proportion of glucose flowing into the renal tubules that is reabsorbed and explain why these are good factoids
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We need to find the urinary inulin concentration. 150 = (60 × Urinary inulin concentration) / 1 Urinary inulin concentration = 150 / 60 Urinary inulin concentration = 2.5 mg/ml So, the urinary inulin concentration is $\boxed{2.5\,\text{mg/ml}}$. b) Show more…
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Adi S.
Inulin is a polysaccharide that happens to be neither secreted nor reabsorbed by the tubules of the kidney, and its molecular weight (5200 daltons) is low enough to permit it to pass freely through the glomerulus. It is infused at a steady rate into the blood of a person whose GFR is to be determined. After a while, a steady-state plasma concentration is achieved. Assume that blood samples taken after steady state has been reached show an inulin concentration of 0.1 g/100 mL of plasma. If a total of 180 mL of urine is collected over the next 2 hr, and analysis shows that there is 0.08 g inulin per mL in the urine, what is the GFR of the person? It is important to note that inulin is not metabolized by the body and is excreted only in the urine.
Inulin is a molecule that is filtered out of the glomerulus but is not secreted or reabsorbed by the renal tubules. If you injected inulin into an animal and after a brief time measured the concentration of inulin in the animal's blood and urine, how could you determine the animal's glomerular filtration rate? Assume that the rate of urine production is 1 milliliter per minute.
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