Potassium Metabolism - Showkat Flashcards
(35 cards)
Where is the majority of K stored?
Intracellularly
What are the major mechanisms for K excretion and the percentages?
Renal (90-5%) and GI excretion (5-10)
What is the concentration of K inside the cell
120-140 meq/dl
What is the internal vs external balance of potassium?
Internal is the regulatino of pot. between ICF and ECF
External is the regulation of total body K through intake and excretion
Where is the only place that K is secreted?
Collecting Duct
What percentage of K is reabsorbed in the PCT?
65%
In the TALH, what transporter is responsible for the movement of K and where is it taking it?
It’s reabsorbing it into the luminal cell by the NaK2Cl transporter
What are the actions of the principal cells?
Bring sodium in from the lumen, use the NaK AtPase pump on the blood side, having the ROMK channel on the lumenal side
Explain the movement of K in relation to aldosterone?
Aldosterone is secreted into the lumenal cell, becoming active and activating the NaK ATPase on the basolateral membrane. This brings 2K into the cell for 3 Na outside, creating a high concentration of K in the cell. Then the Aldosterone also upregulates the activity of ROMK channels, releasing K into the urine.
Explain the relationship between Na, K and having an electronegative lumen
When Na is absorbed from the lumen, it leaves an electronegative lumen, which then makes the K drawn to the lumen to compensate for the loss of + charges
Wht are the three factors affecting K secretion?
concentration gradient electrical gradient (depending on Na reabsorb.) K permeability (ROMK channel depending on alodsterone)
If you Increase the distal delivery of K, what happens to the K secretion? Why?
It increases secretion. This is because of the secreting mechanism that is in place only in the collecting duct
How can you increase K excretion?
Increased K and Na delivery to the distal tubule and CD.
Potassium secretion regulated by aldosterone
What are causes of decreased renal potassium secretion?
renal failure
distal tubular dysfunction
decreased distal tubular flow
hypoaldosteronism
what disorders can lead to increased K secretino
prolong vomiting, nasogastric suction
bartters
gitelmans
hyperaldosteronism
What transport is the main mechanism for regulation of K levels between ICF and ECF
NaK ATPase
What factors affect the internal potassium balance?
plasma potassium concentration
insulin
epinephrine
Acid-Base disturbance
plasma tonicity
cell lysis and cell proliferation
which receptor triggers increased NKATPase activity? Which receptor decreases it?
Beta2 receptors increase (insulin)
Alpha receptors decrease (epinephrine?)
Is hypo or hyper kalemia seen in extracellular alkalosis? acidosis?
in alkalosis, the H has moved into the ecf, pushing the K into the cell, creating hypokalemia of the plasma
in acidosis, the H has moved into the cell, pushing the K into the plasma, causing hyperkalemia
How does plasma tonicity affect K balance?
An increase in plasma tonicity (due to increased Na) will cause K to move into the ECF, to bring water with it. Causing more K to be in the ECF than in the ICF
THEN, loss of intracellular water increases the intracellular K concentration, causing an increased gradient when compared to the ECF. This then causes the K to flow passively out of the potassium channel.
How does cell lysis affect K balance?
When cells lyse, intracellular K is released into extracellular space
How does cell proliferation cause K balance changes?
K is rapidly taken up by proliferating cells, casuses ecf k concentration to fall.
what could cause the cell lysis that leads to an increased K concentration in the ecf?
muscle injury, rhabomyolysis, rbc injury - hemolysis
What are three general causes of hyperkalemia?
Excess Intake
Decreased Renal Excretion
Internal Redistribution
