Solute Transport: Reabsorption and Secretion

Question 1

What is the formula for filtered load?

Answer 1

filtered load (amount/time e.g mg/min) = GFR (V/time e.g ml/min) x Px (amount/volume e.g mg/ml)

Ux: urine concentration of a substance
V: urine flow rate
Px: plasma concentration of a substance

Question 2

What is the formula for net transport rate?

Answer 2

net transport rate = filtered load - excretion rate

0 = no net transport
+ = net reabosorption
- = net secretion

or if filtered load = excretion rate there is no net tubular modification
if filtered load > excretion; net reabsorption
if filtered load < excretion; net secretion

(GFR x Px) - (Ux x V)

Question 3

What is clearance.

Answer 3

the theoretical volume of plasma from which a substance is removed over a period of time

Question 4

What is the formula for clearance?

Answer 4

clearance of x = Excretion rate of x/ Px = (Ux x V)/Px

Ux: urine concentration of x
V: urine flow rate
Px: plasma concentration of x

Question 5

What is the meaning of Tm or transport maximum?

Answer 5

the maximal reabsorption rate of a substance

Question 6

What is the meaning of splay?

Answer 6

splay occurs because some nephrons reach Tm before others; thus Tm not reached yet

Question 7

Normal value for RPF?

Answer 7

600 mL/min

Question 8

Normal value for GFR?

Answer 8

120 mL/min

Question 9

Normal value for FF?

Answer 9

0.20

Question 10

What substance can help you determine effective renal plasma flow?

Answer 10

PAH ( P-aminohippuric acid)

Question 11

Formula for estimating RBF?

Answer 11

RBF = RPF/ 1- HCT

Question 12

What substances are represented in the diagram depicted.

Answer 12

A. protein
B inulin
C. potassium, sodium, urea
D. glucose, bicarbonate
E. PAH
F. creatinine

Question 13

What is the formula for excretion?

Answer 13

Excretion (amount/ time e.g mg/min) Ux x V (mg/mL)