Regulation of K+ Balance Flashcards
What effects does epinephrine have on the extrarenal regulation of plasma K+?
Lowers serum K+ by uptake into the cells of extrarenal tissues
Stimulates K+ excretion by the Kidney
Differs in response for alpha and beta receptors
What does Insulin stimulate that can be used to treat hyperkalemia?
It up regulates Na+K+ATPase
How does aldosterone regulate extrarenal K+?
Causes increased secretion of K+ from the kidneys
Secretion into the interstitial fluid and saliva.
Enhances systemic alkalosis (enhanced cell uptake).
How do B-catecholamines effect K+ uptake?
Breifly describe mechanism.
Increase cell uptake of K+ through increasing cAMP and Na/K ATPase activity.
How does hyperosmolarity influence cell efflux of K+?
Causes it to shift from ICF to ECF (ICF contraction)
Explain how the lumen-positive transepithelial difference is maintained in the proximal tubule?
In the early proximal tubule, Na+ is reabsorbed with bicarbonate.
Cl- is left behind and a negative TEPD builds up
Cl- is repeled out of the lumen and reabsorbed, this combination of NaCl absorption drives water in.
As Cl+ leaves the TEPD becomes more positive.
How is K+ absorbed in the Early convoluted tubule and proximal straight tubule?
Paracellularly
Na+/K+ ATPase and TEPD dependent.
How does a large K+ medullary concentration have an effect on Na+ reabsorption?
Decreases NKCC2 reabsorption by thick ascending loop.
Enhances Na+ delivery to the distal tubule
Stimulates K+ secretion and Na+ absorption
How do principal cells secrete K+?
Reabsorb Na utiliyzing ENaCs
Secrete K using BK channels or ROMK (Renal outer medullary potassium channel.
How do type B intercalated cells secrete K+?
How do they influence acid base/regulation?
Use HK channels to secrete bicarbonate and Potassium.
Retention of H+ as well, together decreasing pH.
How do type A intercalated cells influence potassium regulation and acid/base regulation?
Use HK channels to bring HCO3 and potassium into the capillaries.
Secretes H+, lowering pH.
What are the important factors influencing secretion of K+?
Increased ECF [K+]
Aldosterone
Increased tubular flow rate
What factors regulate buildup of extracellular [K+]?
Increase in Na-K-ATPase pump in basolateral membrane of principle cells
Reduced back-leakage of K+ channels from ICF to renal interstitium
Increased synthesis of K+ channels and insertion on luminal membrane
Increased aldosterone secretion
Increased DT flow rate
What change in flow rate must occur to increase aldosterone?
A lower flow rate
Less Na+ is being brought to the distal tubule and being exchanged.
Alkalemia has what effects on K secretion?
LEADS TO HYPOKALEMIA
Increases Na/K ATPase activity
Increase K concentration in the filtrate
Increased passive diffusion in the tubule lumen
Increased K - secretion
