Muster: K+/Ca++ Homeostasis

Question 1

What 2 primary functions does potassium serve?

Answer 1

1. Cell metabolism

2. The ratio of intracellular/extracellular potassium is the primary determinant of the resting potential of cells

Question 2

What’s the concentration of K+ inside the cells?

Answer 2

140-150 mM

Question 3

What is the extracellular concentration of Na+?

Answer 3

140 mM

Question 4

What % of Potassium is stored intracellularly?

Answer 4

98 %

Question 5

What factors stimulate the Na/K ATPase?

Answer 5

Insulin

Catecholamines

Question 6

What other factors impact shift control?

Answer 6

Plasma K+ (cellular uptake may be increased when serum K rises)

Exercise (muscle cells release K+)

Cell breakdown

Chronic Disease (ex. metabolic acidosis: H+ in cells, K+ gets kicked out)–you have to be very acidotic before this causes hyperkalemia

Question 7

Through what receptors do catecholamines stimulate the Na/K ATPase?

Answer 7

B-2

Question 8

The proximal tubule reabsorbs what percent of K+ and Ca++?
Thick ascending limb?
Intercalated cell?

Answer 8

55-65 % proximal tubule
25 % Thick ascending
10 % Intercalated Cells? (late distal tubule and collecting duct)

Question 9

What do Aldosterone and Angiotensin II do to ROMK?

Answer 9

Aldosterone: increases ROMK going from vessel to membrane

Angiotensin II: Blocks ROMK

Question 10

What blocks ROMK on the intracellular side?

Answer 10

Mg2+

Question 11

When is the BK channel opened?

Answer 11

In high potassium states (so then we ultimately have 2 channels facilitating the excretion of K+; ROMK and BK)

Question 12

In a low potassium diet, there is no activity of ______ channel.

Answer 12

BK channel

Question 13

In a low potassium diet, there is decreased presence of _________channel because there is a decrease in ____________.

Answer 13

ROMK

Aldosterone

Question 14

What two things increase Aldosterone?

Answer 14

Angiotensin II

K+

Question 15

What is the goal of PTH?

Answer 15

Increase serum Ca++

Question 16

What does PTH do to bone?

Answer 16

Stimulates Ca++ and Phosphorous release

Question 17

What does PTH do to the kidneys?

Answer 17

Stimulates Ca++ absorbtion, Vitamin D conversion to active vitamin D, and PO4 secretion

Question 18

What organ activates Vitamin D? How?

Answer 18

Kidney via hydroxylation

Question 19

What does Active Vitamin D do?

Answer 19

Stimulates Increased gut absorption of Ca++

Question 20

PTH responds to what form of calcium?

What % is this of our total calcium?

Answer 20

Free calcium

50 %

Question 21

What is Primary Hyperparathyroidism?

Answer 21

Increase in PTH-It is always on, independently of Ca++

Question 22

What happens to phosphorous as a result of PTH on the kidney?

Answer 22

Decreases renal phosphorus absorption and INCREASES EXCRETION.

Question 23

What happens to Calcium due to PTH?

Answer 23

Increases Ca++ absorption in the kidney.

Question 24

What does Calcium bind to in cells of the distal convoluted tubule?

Answer 24

Calbindin

Question 25

What two transporters are on the basolateral side of the distal convoluted tubule cell?

Answer 25

Ca++ ATPase

Ca2+/Na+ Secondary transporter (Na+ in, Ca++ out)

Question 26

Where does PTH bind?

Answer 26

Basolateral membrane

Question 27

What cell reabsorbs K+ actively?

Where is it?

Answer 27

Alpha-intercalated cell

Right next to the principal cells in the collecting duct

Question 28

What are the 3 ATPases on the alpha-intercalated cell?

Answer 28

Na/K : basolateral membrane
K/H : lumenal membrane
H: lumenal membrane

Question 29

What does active Vitamin D do in the gut?

Answer 29

Stimulates gut absorption of calcium

Question 30

What does “Phosphorous Trashing Hormone (PTH)” help you to remember?

Answer 30

PTH decreases Renal phosphorous absorption (increases excretion!)