GFR Clearance

Question 1

What should NOT be the glomerular ultra-filtrate?

Answer 1

Proteins

Thus making it resemble closely to plasma

Question 2

? mL/min or L/hr is filtered into the tubules

Answer 2

125 mL/min

7.6 L/hr

Question 3

Negative charges of the glomerular membrane

Answer 3

Located the mucopolysaccharide coat of the podocytes

And on the basement membrane

Repel the plasma proteins (also negative)

Question 4

Clearance calculation

Answer 4

(Amt. solute excreted in urine) / (plasma conc. Of solute)

….in other words…

(Urine flow * urine conc of solute) / (plasma conc of solute)

Question 5

If substance is completely cleared in a single pass…

Answer 5

Its extraction is very efficient and thus its clearance is equal to the RENAL PLASMA FLOW

Example of such substance = para amino huppuric acid (PAH)

Question 6

If substance is efficiently reabsorbed … such that the venous and arterial concentration are equal and urine concentration is negligible…

Answer 6

Clearance ~ 0

Glucose

Question 7

If substance is excreted only by means of filtration, filtered without restriction, is not reabsorbed, secreted or metabolized…then

Answer 7

The amount excreted = amount filtered

Creatinine (endogenous)

Inulin, Mannitol and several radiolabelled compounds

For these substances:

GFR = (UF * [urine]) / ([plasma])

Question 8

If clearance of substance is less than GFR….

More than?

Answer 8

Less than —> net reabsorption

More than —> new secretion