K+ and Ca++ Regulation

Question 1

MOA of Insulin on [K+]

Answer 1

Increases the activity of the Na+/K+ ATPase
Promotes skeletal muscle uptake
eat—stimulate insulin—alleviates a sharp rise in [K+]

Question 2

MOA of Catecholamines on [K+]

Answer 2

B2 receptors stimulate Na+/K+ ATPase inducing cellular uptake

Question 3

Other factors that affect [K+]: (3)

Answer 3

1. plasma concentrations
2. exercise- muscle cells release K+ during exercise
3. pH

Question 4

PT excretes how much K?

Answer 4

55-65% via tight junctions

Question 5

Thin Ascending Limb excretes how much K?

Answer 5

25%

Question 6

Principal cells excretes how much K?

Answer 6

10%

Question 7

MOA of Aldosterone (3)

Answer 7

1. increases the activity of Na/K pump
2. increases the presence of ROMK channels
3. Occurs in normal or mildly elevated K+
   * * In very high [K+] the BK channels will open thus facilitating K excretion

Question 8

Where is K+ actively absorbed?

Answer 8

a-intercalated cell

Question 9

MOA of the intercalated cells

Answer 9

1. K+ exchanged for H+
2. Lots of H+ must be processed to reabsorb K+
3. Also req’s the reabsorption of bicarb

Question 10

Calcium homeostasis:

Answer 10

1. 40% of all Ca++ is bound to albumin
2. 10% is bound to other stuff such as phosphate and citrate
3. 50% is available at ionized calcium (free calcium)

Question 11

T/F the PTH responds to the free plasma concentrations?

Answer 11

T

Question 12

Ca++ reabsorption

Answer 12

PT 65% paracellular (tight junctions)
LOH 20-25% (tight junctions)
DT 10% (transcellular)

Question 13

What does Ca++ bind to in the DT?

Answer 13

Calbindin