Calculation of reabsorption and secretion rates

- The reabsorption or secretion rate is the difference between the amount filtered across the glomerular capillaries and the amount excreted in urine. It is calculated with the following equations:

Filtered load = GFR x [plasma] Excretion rate = V x [urine] Reabsorption rate = Filtered load - Excretion rate Secretion rate = Excretion rate - Filtered load

- If the filtered load is greater than the excretion rate, then net reabsorption of the substance has occurred. If the filtered load is less than the excretion rate, then net secretion of the substance has occurred.

Table 5-3. Effect of Changes in Starling Forces on GFR, RPF, and Filtration Fraction

Effect on GFR

Effect on RPF

Effect on Filtration Fraction

Constriction of afferent arteriole

(caused by I PGC)

i

No change

Constriction of efferent arteriole

(caused by T PGC)

I

(T GFRAl RPF)

Increased plasma [protein]

(caused by T tt-qc)

No change

(4- GFR/unchanged RPF)

Ureteral stone

(caused by T PBS)

No change

(1 GFR/unchanged RPF)

GFR = glomerular filtration rate; RPF = renal plasma flow.

GFR = glomerular filtration rate; RPF = renal plasma flow.

Glomerular

Glomerular

Figure 5-4. Processes of filtration, reabsorption, and secretion. The sum of the three processes is excretion.

- Example: A woman with untreated diabetes mellitus has a GFR of 120 ml/min, a plasma glucose concentration of 400 mg/dl, a urine glucose concentration of 2500 mg/dl, and a urine flow rate of 4 ml/min. What is the reabsorption rate of glucose?

Filtered load = GFR x Plasma [glucose] = 120 ml/min x 400 mg/dl = 480 mg/min Excretion = V x Urine [glucose]

= 4 ml/min x 2500 mg/dl = 100 mg/min Reabsorption = 480 mg/min - 100 mg/min = 380 mg/min

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Responses

  • Emilia
    What is renal reabsorption rate?
    2 years ago
  • Michelina
    How to calculate secretion rate of a drug?
    2 years ago
  • andreas
    How to calculate glucose reabsorption?
    2 years ago
  • YVONNE SCHMIDT
    How to calculate reabsorbed substance?
    2 years ago
  • Wolfgang Osterhagen
    How to calculate glucose excretion?
    2 years ago
  • MORGAN
    How to calculate glucose filtration per minute?
    11 months ago
  • charles
    How do you calculate glucose reabsorbed?
    10 months ago
  • Gloria Li Fonti
    How to calculate reabsorption rate of urea?
    10 months ago
  • anni
    How to calculate reabsorption given clearance and excretion rate?
    10 months ago
  • Faramond
    How to calculate reabsorption of solute x in renal?
    9 months ago
  • kiros
    How to calculate excreted load?
    9 months ago
  • marco
    What to do for smooth excretion?
    9 months ago
  • gorbadoc
    How to find excretion rates?
    5 months ago
  • Jonas Eichmann
    What are the equations for clearance, excretion and filtrate load?
    5 months ago
  • fre-qalsi
    How to calculate rate of excresion?
    5 months ago
  • primrose
    How to calculate rate of water reabsorption by tubule?
    4 months ago
  • Rosarmosario
    How to calculate rate of urination?
    4 months ago
  • semere abrha
    How to calculate the rate of urine excreted?
    1 month ago
  • olli
    How to do renal calculation of excretion vs absorbed?
    23 days ago
  • stephan
    How to calculate the percentage of filtrate reabsorbed by the kidney tubules?
    22 days ago

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