Regulation of Electrolytes

Question 1

What would happen if the renal tubules didn’t reabsorb the glomerular filtrate?

Answer 1

The daily salt and water intake would increase

Question 2

What is used to determine renal tubule function?

Answer 2

Calculating Fractional Excretion rate (FER)

Question 3

The net rate of tubular resorption and excretion of a filtered substance is the _____________

Answer 3

FER

Question 4

FER = ?

Answer 4

[urine x ] / ([plasma x ] / [urine creatinine]) / [plasma creatinine] x 100

Question 5

FER of Na = ?

Answer 5

Cattle = <4 %
Horses, dogs, cats = <1%

Question 6

FER of Ca = ?

Answer 6

Horses <33%
Dogs <0.25%

Question 7

FER of K = ?

Answer 7

Horses 15-80%
Dogs <20%
Cats 24%

Question 8

FER of P = ?

Answer 8

horses <0.5%
Dogs <39%
Cats <73%

Question 9

Clinically, the FER will tell you ?

Answer 9

Functional integrity of renal tubules (percentage of a filtered substance being is being excreted)

Question 10

What are the 2 ways solutes can move from the apical to the basolateral side?

Answer 10

Transcellular and Paracellular

Question 11

Which type of solute transport is through either carrier-mediated or active?

Answer 11

Transcellular

Question 12

What 3 things drive the movement of solutes from interstial fluid into blood (peritubular capillary)?

Answer 12

• Starling’s forces
• Peritubular capillaries (increase in oncotic pressure)
• decrease capillary wall resistance (low hydrostatic pressure)

Question 13

On the basolateral side of the proximal tubule, how does Na move?

Answer 13

Na/K/ATPase pump

Question 14

How many Na out for every 2 K in in the PCT?

Answer 14

3

Question 15

On the apical side of the PCT, how does Na move?

Answer 15

With co transporters (Glucose, AA, Citrate) and countertransporters (H)

Question 16

Which ion passively diffuses in the PCT with Na?

Answer 16

K (paracelullarly)

Question 17

What makes the absorption of Na from the PCT in the thick LoH and DCT different?

Answer 17

It goes against the concentration gradient (active transport of Na/K on basolateral side)

Question 18

The NKCC2 cotransporter in the PCT is inhibited by which type of medications? Give an example

Answer 18

Loop Diuretics (ex Furosemide)

Question 19

Which medicatioins inhibit the apical Na/Cl transporter in the DCT?

Answer 19

Thiazide diuretics

Question 20

What is the basolateral transporter in the DCT?

Answer 20

Na/K exchanger

Question 21

List factors that regulate the Na transport

Answer 21

• Angiotensin II
• Aldosterone
• ADH
• NO
• Endothelin-1
• ANP

Question 22

Potassium is mostly absorbed with sodium via which side of the cell (PCT/Thick LoH, CD)?

Answer 22

Basolateral

Question 23

What happens to K in the apical side?

Answer 23

It will leak into the lumen

Question 24

what are the main mechanisms of reabsorption in the proximal tubule?

Answer 24

Paracellular mechanisms

Question 25

In the thick LoH, intracellular K exits to the interstitium via a transporter in which side? (30% of filtered load)

Answer 25

basolateral

Question 26

Which part of the nephron is responsible fro the net renal K secretion?

Answer 26

Collecting duct

Question 27

what 2 things regulate Potassium transport?

Answer 27

- Na regulation - aldosterone (RAAS system)