75-76: TFP Clearance I & II

Question 1

[tubular fluid solute] compared to [plasma solute] is a function of concentration and amount of solutes in tubular
fluid

Answer 1

TF/P

Question 2

What is TF/P dependent upon?

Answer 2

H2O reabsorption along nephron

Question 3

TF/P formula

Answer 3

C = Q/V

Question 4

If more H2O reabsorbed than

solutes or secretion of solute then what is TF/P?

Answer 4

Greater than 1

Question 5

If more solute reabsorbed than H2O then what is TF/P?

Answer 5

Less than 1

Question 6

What is volume of plasma cleared of a particular solute by the kidneys per unit time?

Answer 6

Renal Clearance

Question 7

Renal Clearance formula

Answer 7

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

Question 8

Filtered Load formula

Answer 8

GFR x [P]x

Question 9

Excretion Rate formula

Answer 9

V x [U]x

Question 10

How is glucose transported from tubular lumen into cell?

Answer 10

Na+/Glucose Cotransporter

Question 11

How is glucose transported from cell into capillary?

Answer 11

Facilitated diffusion

Question 12

What is the plasma glucose concentration threshold?

Answer 12

2 mg/mL or (200 mg/dL)

Question 13

What is the maximum transport of glucose?

Answer 13

350-375 mg/min

Question 14

______ clearance can be used as a measure of GFR because its neither absorbed or secreted

Answer 14

Inulin

Question 15

Clinically, what is used to measure GFR instead of Inulin?

Answer 15

Creatinine: (overestimates GFR)

Blood Urea Nitrogen: (underestimates GFR)

Question 16

What are the problems of using Inulin clinically?

Answer 16

Must be infused intravenously

Continual blood sampling required

Chemical analysis cumbersome

Question 17

What are the benefits of using Creatinine instead of Inulin, clinically?

Answer 17

Endogenous (by-product of muscle metabolism)

Released into blood at relatively constant rate (only need one blood sample)

Question 18

REABSORPTION OR

SECRETION RATE = _______ minus ______

Answer 18

Filtered Load minus Excretion Rate

Question 19

______ clearance can be used as an estimate of RPF** because its freely filterable

Answer 19

PAH (Para-Amino-Hippurate)

**(only IF plasma conc. of PAH is less than renal threshold conc.)

Question 20

What is the threshold of unbound PAH plasma concentration?

Answer 20

0.15 mg/mL or (15 mg/dL)

Question 21

What occurs when the unbound PAH plasma concentration is greater than 15 mg/dL?

Answer 21

PAH secreted or excreted

Question 22

What occurs when the unbound PAH plasma concentration is less than 15 mg/dL?

Answer 22

PAH remains in the blood

Question 23

What occurs when the glucose plasma concentration is greater than 200 mg/dL?

Answer 23

Glucose transporters will be oversaturated and glucose will end up in urine

Question 24

Clearance ratio formula

Answer 24

CR = Cx / Cinulin

Cx : clearance of substance

Cinulin: clearance of inulin

Question 25

Cx / Cinulin < 1.0

Answer 25

Clearance of Reabsorbed Solutes

Question 26

Cx / Cinulin > 1.0

Answer 26

Clearance of Secreted Solutes

Question 27

Measures Na+ excreted in urine relative to amount reabsorbed by kidney

Answer 27

Fractional Excretion of Sodium

Question 28

What is the clinical use of Fractional Excretion of Sodium?

Answer 28

Part of evaluation of acute renal failure and oliguria

Question 29

Low fractional excretion of Sodium (<1%)

Answer 29

Na+ retention by kidney (pre-renal disease)

Question 30

High fractional excretion of Sodium (>1%)

Answer 30

``` Na+ wasting due to tubular damage/intrinsic renal failure (acute tubular necrosis) ```

Question 31

Osmolar Clearance formula

Answer 31

Cosm = (Uosm x V) / Posm** **IF Posm is constant (300 mOsm/L)

Question 32

Free water

Answer 32

Solute-free water

Question 33

Method for assessing the ability of kidney to dilute/concentrate urine

Answer 33

Free water clearance

Question 34

Free water clearance formula

Answer 34

CH20= V–(Uosm x V) / Posm

Question 35

CH20= 0 when?

Answer 35

when no solute-free water is excreted **isotonic urine**

Question 36

CH20 is +ve when?

Answer 36

when ADH levels are low, solute-free water is excreted **hypotonic urine**

Question 37

CH20 is -ve when?

Answer 37

when ADH levels are high; all solute-free water is reabsorbed **hypertonic urine**