Regulation of K+ Balance

Question 1

Role of Epi in regulation of plasma K+

Answer 1

Lowers serum K+ by uptake into cells of extrarenal tissues while stimulating K+ excretion by the kidneys.

Question 2

Role of insulin in regulation of plasma K+

Answer 2

Stimulates Na/K ATPase causing a flux of K+ into cells and Na+ out of cells.

Question 3

Insulin and glucose are often used to treat:

Answer 3

Hyperkalemia

Question 4

Role of aldosterone in regulation of plasma K+ (in the kidneys)

Answer 4

Increases K+ excretion by the kidneys

Question 5

Role of aldosterone in regulation of plasma K+ (in the extrarenal tissues)

Answer 5

Increased K+ secretion into intestinal fluids and saliva.

Question 6

Filtered load =

Answer 6

GFR x [plasma] x (% filterability)

Question 7

How does the PCT indirectly affect K+ balance?

Answer 7

Changing the Na+ and Cl- reabsorption has considerable effects on tubular flow and Na+ delivery which impacts K+ later on.

Question 8

What is transepithelial difference? (TEPD)

Answer 8

The voltage difference between 2 sides of a membrane.

Question 9

What is the process of creating a TEPD?

Answer 9

1. Initially Na+ is reabsorbed w/ HCO3-.
2. Cl- remains behind
3. Negative TEPD builds up
4. Cl- is repelled and reabsorbed.
5. NaCl reabsorption drags water along.
6. Positive TEPD builds up as Cl- reabsorbs.
7. Positive TEPd repels K+.
8. K+ reabsorbed paracellularly.

Question 10

What is the goal of medullary recycling?

Why?

Answer 10

Increase presence of medullary K+.
Large K+ presence decreases the NKCC2 reabsorption in the TAL –> enhanced Na-delivery to DCT –> stimulates Na-reabsorption and K-secretion

Question 11

Is K+ secreted or reabsorbed in the late DCT and cortical CD?

Answer 11

BOTH

Question 12

What cells secrete K+? (2)

Answer 12

Principal cells

b-intercalated cells

Question 13

What are the 3 most important factors that stimulate K+ secretion?

Answer 13

Increased ECF [K+}
Aldosterone
Increased tubular flow rate

Question 14

What cells reabsorb K+?

Answer 14

a-intercalated cells

Question 15

2 most important factors affecting K+ reabsorption

Answer 15

K+ deficiency

K+ loss thru severe diarrhea

Question 16

Principal cells reabsorb:

Secrete:

Answer 16

Na+, H2O

K+

Question 17

a-intercalated cells reabsorb:

Secrete:

Answer 17

K+, HCO3-

H+

Question 18

b-intercalated cells reabsorb:

Secrete:

Answer 18

H+, Cl-

K+, HCO3-

Question 19

5 factors that regulate K+ secretion

Answer 19

1. Na/K ATPase
2. Reduced back-leakage of K+ from the ICF to interstitium.
3. • synthesis of K-channels and insertion into luminal membrane.
4. • aldosterone secretion
5. Increased DCT flow rate

Question 20

What is the effect of flow rate on K+ secretion? How?

Answer 20

Increased flow rate = increased K+ secretion

As more Na+ id delivered to DCT, the gradient across the tubular cell rises and K+ is promoted.

Question 21

What is the effect of decreased flow rate on K+ secretion? How?

Answer 21

Decreased flow rate = decreased K+ secretion

K+ conc. builds up early in tubule and decreases the gradient for K+ to move.

Question 22

Why is increased tubular flow rate important in K+ balance?

Answer 22

It helps to preserve normal K+ excretion during changes in Na+ intake and aldosterone levels.

Question 23

What happens in acute alkolosis to K+?

Answer 23

\+ NaK ATPase
\+ diffusion of K+ into lumen
\+ K+ channels
\+ K+ secretion
End result --> hypokalemia

Question 24

What happens in acute acidosis to K+?

Answer 24

• NaK ATPase
• diffusion of K+ into lumen
• K+ channels
• K+ secretion
  End result –> hyperkalemia

Question 25

What happens to K+ secretion in chronic acidosis?

Answer 25

It stimulates K+ secretion

Question 26

``` Factors' affect on K+ secretion ADH Luminal flow rate Acidosis Alkalosis Glucocorticoids Anion delivery ```

Answer 26

``` ADH + Luminal flow rate + Acidosis - Alkalosis + Glucocorticoids + Anion delivery + ```