4. Regulation of Potassium Flashcards
What is an extrarenal regulation of plasma K+ that lowers serum K+ by uptake into cells of extrarenal tissues even while stimulating K+ secretion by the kidney (response differs depending on A/B receptor)
Epinephrine
What stimulates NaKATPase causing a flux of K+ into cells and efflux of Na from cells? Can also treat hyperkalemia
Insulin
What stimulates an increase in K excretion by the kidney and extrarenally stimulates an increase in secretion into intestinal fluids and saliva (enhances acid secretion via alkalosis - K is lo)
aldosterone
What is the calculation for filtered load of any solute?
GFR(V*[U] / [P]) * plasma concentration * (%filterability)
PCT early vs. late… Most H2O, Na, K, Cl, HCO3, Ca, and Pi are reabsorbed here along with 100% glucose and AA. What is the major mechanism for all of the transporting?
Na/KATPase pump in the basolateral membrane
Changing what has considerable effects on distal tubular flow and distal tubular Na delivery, which impacts K+?
Changing NaCl reabsorption
K+ reabsorption is driven by TEPD (transepithelial lumen-positive difference) in the LATE proximal tubule. What are the 7 steps that need to happen in order for there to be a TEPD for K to be reabsorbed?
- Early PT, Na reabsorbed with HCO3
- Cl gets left behind
- Negative TEPD builds up (inside lumen) meaning negative inside, positive on the outside, attracting -
- Cl- is then reabsorped
- Continued NaCl reabsorption drags water along
- Positive TEPD builds up as Cl- reabsorbs (meaning positive inside, negative outside)
- Attracts and repels K to reabsorb paracellularly
In the loop of henle, K is secreted into cortical CD, K is reabsorbed by outer medullary CD and inner medullary CD (OMCD/IMCD). K floats in the interstitium and is secreted into late PT/descending thin limbs of LoH with the mail goal of? Why?
increasing the presence of medullary K+ (medullary recycling)
Large K presence decreases NKCC2 in TAL which enhances Na delivery to distal tubule, stimulates Na reabsorption and K secretion = helps excrete K :)
What occurs to K+ in the late DT and cortical CD ?
depends on the body’s needs, either secretion or reabsorption
The principle cells (ENAC/Kchannel/NaKATPase) and B-intercalated cells(H/KATPase) secrete K+in the distal tubule and collecting duct. The most important factors that stimulate potassium secretion is? (3)
- increased ECF [K]
- aldosterone
- increased tubular flow rate
The A-intercalted cells (all same exchangers just switch apical and baso side) in the distal tubule and collecting duct reabsorb K+. What are the two most important factors that stimulate K reabsorption?
- K deficiency, low k diet, hypokalemia
2. K loss through severe diarrhea
When there is an increased flow rate, why does this enhance K+ secretion?
increases the K concentration gradient and delivers more Na to the DT for reabsorption which will then increase K secretion
When there is a decreased flow rate, why does the K+ secretion slow?
K concentrations build up earlier in the tubule, decreasing concentration gradient between cell and tubular fluid
Sodium intake and aldosteone levels act together to make sure the K+ exceretion remains balance. when there is high na intake, what happens?
Aldosterone decreases which inhibits K secretion in CCD, GFR increases and PCT Na reabsorption decreases, which activates K secretion = balance
Alkalosis is the actue process that decreases H+ ion concentration in the ECF while alkalemia is physiologically high blood pH… what does this do the K secretion?
increases NaKatpase, increases [k], increases k channels and secretion resulting in hypokalemia (K is lo)
inc in pH = more K excreted
