Physiology Osborn Renal Ps4: Renal Transport: Formation Of Urine

Front 1

1. Glucose transport via the apical SGLUT symport is an example of

A. simple diffusion
B. facilitated diffusion
C. secondary active transport
D. paracellular transport
E. Pinocytosis

Back 1

C – secondary active transport

Front 2

2. The secretion of PAH and the reabsorption of glucose are similar in that

A. both require a Na+/K+ ATPase on the basolateral membrane
B. both substance will appear in the urine only at high plasma concentrations
C. both require a Na+/K+ ATPase on the apical membrane
D. transport rate of both is independent of the filtered load
E. transport of both occurs throughout the entire length of the nephron

Back 2

A. both require a Na+/K+ ATPase on the basolateral membrane

both use the gradient established by the Na+/K+ ATPAse to provide the energy for other cotransporters.

This ATPase is located on the basolateral membrane, not on the apical membrane.

Front 3

3 In the proximal tubule, urea reabsorption occurs by

A. passive diffusion through the membrane
B. facilitated diffusion using a uniporter
C. primary active transport (ATPase)
D. secondary active transport
E. pinocytosis

Back 3

B. facilitated diffusion using a uniporter

Front 4

4. Which of the following would be described as paracellular transport?

A. water and solutes flowing from the interstitium into the peritubular capillaries
B. water and solute flowing through the tight junctions between epithelial cells
C. solute transported across the cell membrane down a concentration gradient
D. solute transported across the cell membrane against a concentration gradient
E. water or solute transported across the cell membrane through channels

Back 4

B. water and solute flowing through the tight junctions between epithelial cells

Front 5

6. An important feature common to all epithelium is

A. tight junctions between cells
B. microvilli
C. basolateral folds
D. extensive mitochondria
E. extensive paracellular transport

Back 5

A. A. tight junctions between cells

All epithelial cells are linked by tight junctions. The other features are optional – review PSL431, basic properties of epithelial cells.

Front 6

7. Select the statement below which correctly compares normal plasma and urine solute composition
A. plasma[glucose] is usually the same as urine[glucose]
B. plasma[albumin] is usually less than urine[albumin]
C. normal plasma[Na+] has a wider range than in the urine
D. normal osmolarity of plasma has a narrower range than osmolarity of urine
E. pH plasma is usually less than pH of urine

Back 6

D. normal osmolarity of plasma has a narrower range than osmolarity of urine

Normally, there is essentially no glucose and no albumin in the urine. The range for plasma [Na+] and
osmolarity are tightly regulated but excreting different amounts of Na+ and other solute in the urine, so these ranges in the urine are quite large. Urine is normally acidic

Front 7

8. All of following would increase the plasma concentration of urea EXCEPT?

A. decrease in GFR
B. high protein diet
C. blocking the urea cotransporter
D. decreased ECF volume.

Back 7

C. blocking the urea cotransporter

Urea does not have a cotransporter. Urea is a byproduct of amino acid metabolism, and will increase when the diet includes more proteins (this is one of the potential problems when using urea levels as an indicator of GFR).

Front 8

9. A rise in the steady state plasma concentration of which solute is used clinically to indicate a fall in GFR?

A. creatinine
B. PAH
C. inulin
D. glucose
E. Na+

Back 8

A. creatinine

Both creatinine and urea are used in this way. Creatinine is more reliable, because the production of
creatinine tends to be less variable than the production of urea

Front 9

10. A man is in steady state balance with respect to urea, which means that his production of urea each day is the same as his excretion of urea each day.
His intake, GFR and urine flow rate is given below
GFR 170 L/day
Plasma [urea] 10 mg/dL
Urea production 8.5 gm/day
Urine flow 1 L/day

Find the following:
Urine excretion rate of urea
Concentration of urea in the urine
How much urea is filtered each day
How much urea is reabsorbed each day
What is the fraction of urea reabsorbed each day

Back 9

10.
Urine excretion rate
8.5g/day

Urine excretion rate = (concentration in urine)* (rate of urine flow)

However, in this case, you know that the individual is in urea balance, and is excreting the same amount each day that is produced. The amount produced each day is 8.5g/day, so the excretion rate is also 8.5g/day (excretion rate should have the units of mass/time)

Concentration of urea in the urine
8.5g/L

Concentration of urea in the urine:
Concentration = amount/ volume
For each day, Amount = 8.5 g (this is the amount excreted each day to remain in balance)
Volume = 1L
Concentration = 8.5g/L

How much urea is filtered each day
17000mg/day

How much is filtered each day
Filtered = rate of filtration of the plasma * concentration of urea in the plasma
= GFR * plasma[urea]
= 170L/day * 10mg/dL * 10dL/L = 17000 mg/day

How much urea is reabsorbed each day
8.5g/day

How much urea is reabsorbed each day
Reabsorption = (amount filtered each day)- (amount excreted each day)
= 17000mg/day – 8.5g/day
=8.5g/day

What is the fraction of urea reabsorbed each day
50%

Front 10

11. The excretion rate of a drug was 10 mg/min. The drug is reabsorbed, and the reabsorption rate was 10mg/min. Plasma concentration of the drug was 10 mg/dl. The GFR was:
a. 100 ml/min
b. 200 ml/in
c. 300 ml/min
d. 350 ml/min
e. 400 ml/min

Back 10

b. 200 ml/in

This drug is reabsorbed, which means that the amount that is excreted is less than the amount that is filtered

Excretion rate= filtration rate – reabsorption rate
Or, filtration rate= excretion rate+reabsorption rate
Filtration rate is the same as filtered load, which is GFR * plasma[drug]
GFR= (urine excretion rate + reabsorption rate)/ Plasma[urea]
= (10mg/min + 10mg/min) / (10mg/dl)
= 20mg/min / 10mg/dl = 2dl/min or 200 ml/min

Front 11

15. A 25 year old man weighing 60 kg has a plasma [creatinine] of 1.4 mg/dL

A 24 hour urine collection is done to determine his creatinine clearance, and thereby estimate
his GFR. The following data are obtained:
Urine [creatinine] = 833 mg/L
Urine volume = 45 ml/ hour

What is his creatinine clearance?

A. 25.9 dl/hr
B. 75.6 dl/hr
C. 25.9 mg/hr
D. 26.8 mg/hr
E. 26.8 dL/hr

Back 11

E. 26.8 dL/hr

Clearance [creatinine] = urine [creatinine] * urine flow / plasma [creatinine]
=( 833mg/L * 1L/1000ml * 45ml/hr)/ (1.4mg/dL)= (37.4 mg/hr)/ (1.4mg/dL) = 26.8 dL/hr

Clearance is a rate. It is the virtual volume of plasma cleared of the solute per time, so the units must be
volume/time, and cannot be mg/hr

Front 12

16. Substance X is freely filterable and is neither metabolized nor stored in the kidney. The plasma concentration of X was 500 mg/dl and 250 mg/min appeared in the urine. The inulin clearance was 100 ml/min. The tubular reabsorption of X was:

a. 25 mg/min
b. 250 mg/min
c. 5 mg/min
d. 50 mg/min
e. 50 mg/min

Back 12

b. 250 mg/min

Reabsorption rate = filtration rate – excretion rate
Filtration rate = filtered load = GFR*plasma[X]
GFR is the same as the clearance of inulin, which is given in the problem as 100ml/min
So filtered load = 100ml/min * 500mg/dL * 1dL/100ml = 500mg/min

Excretion rate = (urine[x]*urine flow rate) = 250mg/min (this is given in the problem)
Reabsorption rate = 500m/min – 250mg/min = 250mg/min


You are investigating the renal handling of a substance, “P”
Unine [P] 360 mg/L
Urine flow rate 1.0 dL/hr
Plasma[P] 4mg/L
GFR 120ml/min

Front 13

18. What is the filtered load of a substance P, where the
A. .48 mg/min
B. 30mg/L
C. 300mg/min
D. 4g/min
E. 4mg/L

Back 13

A. .48 mg/min

Filtered load = GFR * P[x]
Filtered load = 120ml/min* 4mg/L * 1L/1000mL = .48mg/min.

The urine flow and urine concentration values are not relevant for this part of the problem.

Front 14

You are investigating the renal handling of a substance, “P”
Unine [P] 360 mg/L
Urine flow rate 1.0 dL/hr
Plasma[P] 4mg/L
GFR 120ml/min

19. What is the clearance of P?
A. 220 L/day
B. 2.2 L/day
C. 9 mg/day
D. 18 mg/day
E. 9 L/hr

Back 14

E. 9 L/hr

Clearance = (360mg/L * 1.0 dL/hr * 10dL/L) / 4mg/L
= 9L/hr

Front 15

You are investigating the renal handling of a substance, “P”
Unine [P] 360 mg/L
Urine flow rate 1.0 dL/hr
Plasma[P] 4mg/L
GFR 120ml/min

20. What is the type of transport for P?

A. filtered but not reabsorbed or secreted
B. filtered and reabsorbed
C. filtered and secreted
D. not filtered

Back 15

C. filtered and secreted

There are two ways you could determine the type of transport. You could compare the filtered load (amount filtered per time) with the rate at which it is excreted in the urine (urine[p] * urine flow rate).

If the excretion rate is greater than the filtered rate, then the substance is secreted; if the excretion rate is less than the filtered rate, then the substance is reabsorbed.

Front 16

21. All of the following statements regarding renal clearance of a substance are true EXCEPT

A. the greater the excretion rate of a substance, the greater the clearance
B. Clearance designates the concentration of the substance in the urine
C. clearance of a substance that is secreted will be greater than clearance of a substance that is reabsorbed
D. the units of clearance are vol/time
E. a substance that is reabsorbed will have a clearance rate lower than the GFR

Back 16

B. Clearance designates the concentration of the substance in the urine

Front 17

22. Select the correct order of clearances for creatinine, PAH, and X, if X is freely filtered and reabsorbed.

A. creatinine > PAH> X
B. PAH>X> creatinine
C. creatinine > X > PAH
D. PAH > creatinine > X
E. X > PAH > creatinine

Back 17

D. PAH > creatinine > X

If X is freely filtered, and reabsorbed, then the clearance of X will be less than the GFR, and therefore, less than both clearance of creatinine and clearance of PAH.

Front 18

What is the concentration plasma and concentration urine of Cells?

Back 18

concentration plasma: 40-50% by volume (hematocrit)

concentration urine: 0 (because not normally filtered)

Front 19

What is the concentration plasma and concentration urine of Protein (albumin + globulin)

Back 19

concentration plasma: 6-8 g/dL

concentration urine: 0 (because not normally filtered)

Front 20

What is the concentration plasma and concentration urine of Electrolytes: Na+

Back 20

concentration plasma: 135-150mmol/L

concentration urine: 50-130mmol/L (varied w/ homeostatic mechanisms)

Front 21

What is the concentration plasma and concentration urine of Electrolytes: K+

Back 21

concentration plasma: 3.5-5.3mmol/L

concentration urine: 20-70mmol/L (varied w/ homeostatic mechanisms)

Front 22

What is the concentration plasma and concentration urine of Electrolytes: Cl-

Back 22

concentration plasma: 98-110mmol/L

concentration urine: 50-130mmol/L (varied w/ homeostatic mechanisms)

Front 23

What is the concentration plasma and concentration urine of Electrolytes: H+ as pH)

Back 23

concentration plasma: 7.34-7.36

concentration urine: 5.0-7.0 (varied w/ homeostatic mechanisms

Front 24

What is the concentration plasma and concentration urine of Nutrients: glucose

Back 24

concentration plasma: 70-110mg/dL

concentration urine: 0 (100% re-absorption back into plasma)

Front 25

What is the concentration plasma and concentration urine of Waste products: Urea nitrogen

Back 25

concentration plasma: 7-22 mg.dL (2.5-7.8mmol/L)

concentration urine: 200-400mmol/L (varied but a steady rate where excretion = production)

Front 26

What is the concentration plasma and concentration urine of Waste products: Creatinine

Back 26

concentration plasma: 6-20mmol/L

concentration urine: 0.5-1.2 mg/dL (varied but a steady rate where excretion = production)

Front 27

What is the concentration plasma and concentration urine of Waste products: Urobilinogen*

Back 27

concentration plasma: None

concentration urine*: <1mg/dL (varied but a steady rate where excretion = production)

* the pigment in urine is urobilinogen, a breakdown product of bilirubin. Normally, bilirubin is not found in urine

Front 28

What is the concentration plasma and concentration urine of Osmolarity

Back 28

concentration plasma: 280-315mosm/L

concentration urine: 200-400mosm/L

Front 29

What are the two types of magnitude of transport of urine?

Back 29

1. Filtration rate = “filtered load”

2. Excretion rate

Front 30

What is a filtered load?

Back 30

amount of substance filtered per unit time

Front 31

What is the equation for a filtered load?

Back 31

Filtered load = GFR * P[x]
P[x]= concentration of substance in plasma

Front 32

Ultrafiltrate enters _____ _______, then enters
_______ ______.

Back 32

Bowman’s capsule

proximal tubule

Front 33

What is the equation for Excretion rate?

Back 33

Excretion rate = U[x] * V

V= urine flow rate,
U[x] = concentration of substance in urine

Front 34

What is Excretion rate?

Back 34

Elimination from the body as urine

Front 35

If (excretion rate ) < (filtered load), then the substance is?

Back 35

reabsorbed

Front 36

Reabsorption will involve various?

Back 36

transport mechanisms

Front 37

What is the path of reabsorption from the lumen of the tubules to into the capillaries?

Back 37

Reabsorption will involve various transport mechanisms from the lumen of the tubules, across of through the epithelium of the tubules, into the interstitial fluid, and into the capillaries (cortical peritubular, or vasa recta)

Front 38

What is the formula for Reabsorption rate?

Back 38

Reabsorption rate = filtered load – excretion rate

Front 39

If (excretion rate )> filtered load, then substance is?

Back 39

secreted

Front 40

What is the path of secretion?

Back 40

the path of secretion will involve various transport mechanisms from the:

peritubular capillaries (cortical or vasa recta),
into the interstitial fluid,

and

then across or through the tubular epithelium

Front 41

What is the formula for Secretion rate?

Back 41

Secretion rate = excretion rate – filtered load

Front 42

What are the 8 different areas of the nephron?

Back 42

1. Glomerulus
2. Proximal tubule
3. Thin loop of Henle
4. Thick ascending loop of Henle
5. JG apparatus
6. Distal convoluted tubule
7. Connecting tubule segment
8. Collecting duct

Front 43

What happens in the Glomerulus during the transport processes in the nephron?

Back 43

formation of ultrafiltrate

Front 44

What happens in the Proximal tubule during the transport processes in the nephron?

Back 44

bulk reabsorption of water and solute, Na+, K+, Cl-, glucose, amino acids…

Front 45

What happens in the Thin loop of Henle during the transport processes in the nephron?

Back 45

maintenance of interstitial hyperosmotic gradient

Front 46

What happens in the Thick ascending loop of Henle during the transport processes in the nephron?

Back 46

reabsorption of Na, K, Cl-; dilution of tubular fluid

Front 47

What happens in the JG apparatus during the transport processes in the nephron?

Back 47

regulation of GFR and systemic blood pressure

Front 48

What happens in the distal convoluted tubule during the transport processes in the nephron?

Back 48

reabsorption of Na, Cl- divalent cations, dilution
of tubular fluid

Front 49

What happens in the connecting tubule segment during the transport processes in the nephron?

Back 49

regulation of acid, HCO3-, Ca++, Na, K, and
water excretion

Front 50

What happens in the Collecting duct during the transport processes in the nephron?

Back 50

regulation of acid, HCO3-, Na, K, and water excretion

Front 51

What does reabsorption of nutrients happen in the nephron and an example?

Back 51

Proximal tubule

Example: glucose, a saturatable (Tm ) process

Front 52

How is glucose reabsorbed in the proximal tubule?
Include side or area.

Back 52

1. Basolateral Na+/K+ ATPase (in the mitochondria) establishes a gradient for Na+

- lumen side

2. The gradient drives the Na+-dependent symport
on the apical membrane Na+/Glu symport (and the 2nd active transport is SGLUT)

- Epithelial cell

3. A uniporter on the basal side transports glucose
along its gradient ( and a facilitated diffusion of GLUT)

- Blood side

Front 53

What are the plasma [glucose] ranges?

Back 53

from 90mg/dL increasing to over 100mg/dL after meals.

Front 54

Glucose is ________ filtered, and at normal concentrations, ______ ________reabsorbed

Back 54

freely
almost completely

Front 55

The rate limiting step of the glucose reabsorption in the proximal tubule is …………., which has?

Back 55

the symport SGLUT

a maximum rate Tm.

Front 56

The Filtered load of glucose across the glomerular capillaries is directly proportional to ___ & ____?

Back 56

GFR & the plasma [glucose]

Front 57

What is the filtered load of glucose formula and what are the typical GFR and P[glu]?

Back 57

Fglu= GFR * P[glu]


Typical numbers: GFR= 125ml/min
P[glu]= 100mg/dl,

Reabsorption rate: P[glu]= < 400 mg/dl @ filtered load 400mg/min

filtered load = 125mg/min
at this load, all of the glucose is reabsorbed

Front 58

Reabsorption reaches a maximum rate @?

Back 58

Tm

Front 59

What decides the Tm of reabsorption of glucose?

Back 59

There is a limit to the number of Na-glucose transporters on each proximal tubule cell, in each nephron

Front 60

Most cellular nutrients (amino acids, other sugars, vitamins, etc.) are _______ filtered, and typically reabsorbed in ____________ using similar mechanisms.

Back 60

Freely

the proximal tubule

Front 61

Most cellular nutrients (amino acids, other sugars, vitamins, etc.) are freely filtered, and typically reabsorbed in the proximal tubule, using similar mechanisms. What are the 4 most common similarities?

Back 61

Most use a Na+ symport (Apical)

Most have a Tm (maximal rate, saturable rate)

Most are specific (I,.e., some but not all of the amino acids)

Many are inhibited by drugs.

Front 62

Glucose in the urine is a common finding for?

Back 62

a Type I diabetic patient (diabetes mellitus , “mellitus” = honey)

Front 63

A young woman with Type I diabetes, and uncontrolled plasma glucose levels, is ecreting glucose in her urine.

Plasma [glucose] 300mg/dL
Urine[glucose] 5mg/dL
Urine flow [U] 2ml/min
GCF 100 ml/min

Find the following:

Filtered load

Excretion rate

Reabsorption rate

What is the Tm for glucose in this woman?

Back 63

Filtered load

GFR x P[glu]
= 100 ml/min x 300 mg/dl x 1 dl/ 100 ml
= 300 mg/min


Excretion rate

[U] x U[glu]
= 2 ml/min x 5 mg/dl x 1dl/100 ml
= 0.1 mg/min

Reabsorption rate

Filtered – Excrited
= 300 mg/min - .1 mg/min
= 299.9 mg/min


What is the Tm for glucose in this woman?

Reabsorption rate

Filtered – Excrited
= 300 mg/min - .1 mg/min
= 299.9 mg/min

Front 64

Describe the Secretion process in the proximal tubules and an example?

Back 64

Some waste products, including breakdown products of administered drugs, are secreted by the kidney.

Example: PAH is an organic anion

Front 65

Describe the Secretion process of PAH in the proximal tubules?

Back 65

It is freely filtered at the glomerulus, and is secreted in the proximal tubule, so the mechanism involves taking PAH from the interstitium into the cell, then transporting it from the cell into the tubular lumen

Front 66

Proximal tubule cell secretion is?

Back 66

Reabsorption just backwards

Front 67

How is PAH secretion in the proximal tubule?
Include side or area.

Back 67

1. Basolateral Na+/K+ ATPase (est. gradient of NA)

- Blood side


2. Basolateral symport, and antiport
(Tertiary active transport)

- epithelial cell

Using ATPase energy on the basolateral side
Lumen of cap into the cell


3. Apical transporters –facilitated exchange

Front 68

Excretion rate = ?

Back 68

filtered load + secretion rate

Front 69

PAH is used to measure?

Back 69

renal plasma flow.

Front 70

Many other organic anions are secreted in a similar manner, using a Tm limited system, including?

Back 70

endogenous anions (bile salts, urate, fatty acids) ,

and

drugs (acetazolamide, penicillin, saccharin)

Front 71

Penicillin is often used in conjunction with another organic anion that competes with the penicillin transporter – why?

Back 71

So other anions are secreted and penicillin stays in the blood stream longer

Front 72

Transport of Urea can use two types of diffusion. What are they.

Back 72

Paracellular diffusion and Facilitated diffusion

Front 73

Urea can be reabsorption and secretioned, depending on the segment of the nephron, but the net transport is?

Back 73

reabsorption.

Front 74

What is urea?

Back 74

Urea is the end product of amino acid metabolism

Front 75

What are the steps in the formation of Urea?

Back 75

1. Amino acids are first deaminated, producing ammonia (NH3)

2. Ammonia is toxic if accumulated. Enzymes in the liver convert ammonia into urea, a less toxic form of nitrogen.

3. Urea is then excreted by the kidney.

Front 76

Over the long term, urea excretion must match urea production, or ……….occurs, but over the short term, urea excretion varies with?

Back 76

uremia (toxic levels of urea)
diet and water and salt homeostasis

Front 77

What is the mechanism of how Urea is handled by the kidney?

Back 77

1. Proximal tubule: diffusion and solvent drag.

2. Water is reabsorbed, carrying some urea with it (solvent drag). Reabsorption of water increases the concentration of solutes remaining
in the lumen

3. (concentration = amount / volume)
increased concentration ~~> gradient for diffusion between cells (paracelullar)

4. Reabsorption is driven by the increased concentration resulting from reabsorption of water

Front 78

Net gain or loss over Urea in the kidneys and how much?

Back 78

Net = reabsorption,

typically about 50% of the filtered load; or about 50% of the filtered load is excreted

Front 79

Urea is relatively impermeable to most cell membranes, but most cells contain?

Back 79

urea transporters which facilitate diffusion.

Front 80

A rise in plasma [urea] can indicate a fall in the GFR – why?

Back 80

Suppose, GFR drops by 50% (clot in renal artery, e.g.)

Filtered load = GFR * plasma[urea]

Initially, filtered load will decrease by about 50%

Approx 50% filtered load is excreted

Amount excreted/time is now excrete less total

Then Plasma [urea] increases

Front 81

Urea in the blood = BUN (blood urea nitrogen), is often used clinically as an indicator of?

Back 81

GFR.

Front 82

An elevated BUN is often the result of …….. however, elevated BUN can also result from what two things?

Back 82

a falling GFR,


increased urea production (high protein diet, GI bleeding, corticosteroid therapy)

or from decreased volume (such as increased Na and water reabsorption from proximal tubule).

Front 83

What is often referred to as prerenal azotemia, and is generally no associated with a parallel rise in plasma creatinine?

Back 83

BUN (blood urea nitrogen)

Front 84

Is Creatinine filtered, reabsorpbed, and/or secreted?

Back 84

filtered, not reabsorbed, slightly secreted

Front 85

Creatinine can be used to measure?

Back 85

GFR

Front 86

Creatinine is a waste product meaning what of production vs. elimination?

Back 86

normally the amount produced/ day = amount excreted/ day

Front 87

if GFR changes, then what will happen to the the plasma[creatinine]?

Back 87

As with urea, if GFR changes, then the plasma[creatinine] will also change

Front 88

Plasma [creatinine] can be used to estimate GFR just like BUN, but Plasma [creatinine] is more reliable than BUN because?

Back 88

BUN changes more with diet, various hormones, and with water and salt homeostasis.

Front 89

How can we measure the rate at which the kidneys remove a substance from the blood?

Back 89

Depends on:

Reabsorption and/or secretory processes in the tubules

Filtered load – GFR and plasma [substance]

And RPF

Front 90

When we look the rate at which the kidneys remove a substance from the blood, The effect of RPF and GFR is to?

Back 90

determine the amount of solute presented to the cells of the tubules.

Front 91

When the cells of the tubules determine the amount of solute presented to them, they can do one of three things?

Back 91

reabsorb the material, so that it reenters the blood;

secrete more of the substance into the tubules,

or do nothing further to the material once it is filtered.

Front 92

During clearance, waste products can be removed from the blood by …….. & ……..; nutrients can be returned to the blood by?

Back 92

filtration and secretion

reabsorption.

Front 93

Clearance is?

Back 93

measure of efficiency with which the kidney handles a solute.

Front 94

Give the steps of general clearance:

Back 94

1. arterial plasma separates plasma into filtered and not filtered
2. a fraction of plasma that is filtered is either cleared to be reabsorbed or excreted in the urine
3. a fraction of plasma that is filtered and all the plasma that is not filtered reabsorbed and added back to the plasma
4. Plasma leaves the kidney, but solutes are of course, evenly distributed

Front 95

Clearance of PAH?
Filtered?
Reabsorbed?
Secreted?

Back 95

Clearance of PAH?
Filtered: Yes
Reabsorbed: No
Secreted Yes; entirely

Vol/time cleared = vol. plasma delivered/min = RPF

Front 96

Clearance of inulin?
Filtered?
Reabsorbed?
Secreted?

Back 96

Clearance of inulin?
Filtered: Yes
Reabsorbed: No
Secreted: No

Vol/Time ~~> Urine = GFR

Front 97

Clearance of glucose?
Filtered?
Reabsorbed?
Secreted?

Back 97

Clearance of glucose?
Filtered: Yes
Reabsorbed: Yes; all of it
Secreted: No

Nothing is cleared because nothing goes to urine

Front 98

What is the clearance of a substance, X, using the same conservation of mass equations:

Back 98

Amount in = amount out

P[X]a * Cx = (P[X]v * RPFv) + (U[X]) * V)


P[X]a = arterial concentration of X (mg/ml)

Cx = virtual volume of plasma cleared of x/
min (ml/min)

P[X]v = venous concentration of X (mg/ml)

RPFv = renal venous plasma flow (ml/min)

U[X] = urine concentration of X (mg/ml)

V= urine flow (ml/min)

Front 99

P[X]a * Cx is _____ = (P[X]v * RPFv) is ______ and (U[X]) * V) is_____.

Back 99

Arterial
Venous
urine

Front 100

For clearance, we are looking for the “virtual volume” (Box D: in the urine) of plasma which is cleared of solute.

P[X]a * RPFa = (P[X]v * RPFv) + (U[X]) * V)

So, instead of using P[X]a * RPFa as the amount in, we use?

Back 100

P[X]a * Cx


P[X]a * Cx = P[X]v * RPFv + Ux * V

Front 101

In Clearance formula:

P[X]a * Cx = (P[X]v * RPFv) + (U[X]) * V)


If the volume is cleared (all of X is removed), the output is just urine excretion:

Formula for urine that hasn’t been cleared is?

Back 101

P[X]a * Cx = P[X]v * RPFv + Ux * V

Front 102

In Clearance formula:

P[X]a * Cx = (P[X]v * RPFv) + (U[X]) * V)


If the volume is cleared (all of X is removed), the output is just urine excretion:

Formula for urine that has been cleared is?

Back 102

P[X]a * Cx = 0 + Ux*V

Front 103

In the Clearance formula, Cx = ?

Back 103

U[X] * V / P[X]a

Front 104

This is not a real volume, it is not a mass,
but it is a virtual volume used to quantify kidney function.

U[p]= 360mg/L
V= 0.1L/hr
P[p]= 4mg/L
C[p] = ??

For example, Solute p is?

Back 104

C[p] = U[p] x V / P[p]

= 360 mg/L x 0.1L/hr / 4mg/L
= 36 mg/hr / 4 mg/L
= 9 L/hr

Front 105

The following data were obtained on a 50 Kg. patient during a renal function test:

Plasma
PAH – 2.0 (mg/dl)
Inulin – 94.7 (mg./dl)
Creatinine – 0.8 (mg/dl)
Urea (BUN) - 10 mg/dl

Urine
PAH - 226 (mg/dl)
Inulin - 3500 (mg./dl)
Creatinine - 30 (mg/dl)
Urea (BUN) - 6.9 mg/dl

Urine flow (V) = 2.3 ml/min
1. Calculate the clearance of urea

2. Is this greater or less than the GFR ?

3. The individual is taking a drug for treatment of cancer. The clearance of this drug is 200ml/min

Back 105

1. Calculate the clearance of urea

U[urea] x V / P[urea]
= 6.9 mg/dl x 2.3 ml/min x 1 dl/100 ml / 10 mg/dl
= .016 dl / min or 1.6 ml/min

2. Is this greater or less than the GFR ?

C (in) = I [urine] x V / I [plasma]
= 3500 (mg/dl) x 2.3 ml/min x 1 dl/100 ml / 94.7 (mg./dl)
= .85 dl/min or 85 ml

less causing reabsorption

3. The individual is taking a drug for treatment of cancer. The clearance of this drug is 200ml/min

Front 106

Why is knowing the clearance of this drug important?

Back 106

It determines the plasma concentrations over time. If secreted, you must keep giving drug to keep steady concentration