Handling of Potassium

Question 1

K+ is the main cation in the ______ (ECF/ICF)

What is the significance?

Answer 1

ICF

-maintains the membrane potential

Question 2

What can diabetes mellatus cause hyperkalemia?

Answer 2

Because usually insulin cause an uptake of K+ ions into the cell, so if there is a lack of insulin, there will be more K+ in the blood than in the cell which would result in hyperkalemia

Question 3

Effect of beta-2 agonists on K+ levels in the blood

Answer 3

They will cause decreased amt of K+ in the blood (hypokalemia) because they enhance the Na+/K+ ATPase

Question 4

Effect of alpha-1 agonists on K+ levels in the blood

Answer 4

They will cause increased amt of K+ in the blood (hyperkalemia) because they inhibit the Na+/K+ ATPase

Question 5

What would result following cell lysis (hypo or hyperkalemia)?

Why?

What physiological consequences may occur?

Answer 5

Hyperkalemia would result because K+ is dominant in the ICF, so when the cell ruptures, lots of K+ ions will be released in the blood

Can causes muscle weakness, arrhythmias

Question 6

How could exercise result in hyperkalemia theoretically?

Answer 6

During exercise, ATP stores are used up which will cause a decrease in the activity of the Na+/K+ ATPase pump resulting in a build up of K+ in the blood

Question 7

K+ reabsorption is done mainly by which transported in which part of the nephron

Answer 7

K+/H+ exchanger in the alpha intercalated cells in the distal tubule/collecting duct

Question 8

Effect of aldosterone on K+

Answer 8

Aldosterone causes an increase in K+ secretion because if the increase in Na+ reabsorption and there is also an increase in the luminal K+ channels

Question 9

Does alkalosis or acidosis cause a K+ secretion?

Why?

Answer 9

Alkalosis causes K+ secretion because H+ will be moved into the cell (eventually blood) so K+ is transported the other directionn (secreted)

Question 10

is aldosterone stimulated by increased or decreased K+

Answer 10

Increased K+ stimulates aldosterone which is why it causes K+ secretion

Question 11

K+ excretoin depends on K+ secretion from which cells?

Is it done passively or actively?

Answer 11

Principal cells

• done passively

Question 12

What are the values of potassium that determine hyper/hypokalemia?

Answer 12

> 5.0 mEq/L = hyperkalemia

<3.5 mEq/L = hypokalemia

Question 13

In which two parts of the nephron and which transporters require energy to transport K+

Answer 13

• intercalated cells (H+/K+)

- thick ascending limb (Na+/K+/Cl-)

Question 14

What are two types of special channels that allow potassium ions to rapidly diffuse across the membrane of principal cells?

Answer 14

(1) The renal outer medullary potassium (ROMK) channels

(2) high conductance “big” potassium (BK) channels.