K+ Regulation Flashcards
1
Q
- Normal serum K+
A
3.5-5.0 mEq/L
2
Q
- Role of epinephrine in the regulation of K+
A
- Lowers serum K+ by uptake into cells of extrarenal tissues
- Stimulates K+ excretion in the kidney
- Differing response for alpha versus beta stimulation
3
Q
- Role of insulin in the regulation of K+
A
- Stimulates Na+/K+ ATPase causing a flux of K+ into cells and efflux of Na+ out of cells
- Can be used with glucose to treat hyperkalemia
4
Q
- Role of aldosterone in regulation of K+
A
- Renal: Increase in K+ excretion
- Extrarenal: INcreased K+ secretion into intestinal fluids and saliva
- Enhances acid secretion via production of systemic alkalosis
5
Q
- Hypokalemia is associated with which change in acid base balance?
A
HypOkalemia is associated with AlkaLOSIS
6
Q
- Insulin efect on K+
- Mechanism
A
- Enhanced cell uptake
- Na+/K+ ATPase
7
Q
- Beta catecholamines effect on potassium
- Brief mechanism
A
- Enhanced cell uptake
- Increased activity of the Na+/K+ ATPase via increased activation of cAMP
8
Q
- Alpha catecholamine effect on K+
- Brief mechanism
A
- IMPAIRED cell uptake
- Decreasing activity of the Na+/K+ ATPase via inhibition of cAMP
9
Q
- Acidosis effects on K+
- Brief mechanism
A
- IMPAIRED cell uptake
- Donnan effect;inhibition of the Na+/K+ ATPase
10
Q
- Alkalosis effects on K+
- Mechanism
A
- Enhanced cell uptake
- “k is lo” alkalosis
11
Q
- External K+ balance effect on K+
- Mechanism
A
- Loose correlation
- Ratio vs total body K+ until severe states
12
Q
- Hyperosmolarity effect on K+
- Mechanism
A
- Enhanced cell efflux
- D/t contraction of ICF volume and increased intracellular [K+]
13
Q
- Strenous exercise effect on K+
- Mechanism
A
- Enhanced cell efflux
*
14
Q
- Insulin and catecholamines activate which transporters? (MORE THAN ONE!)
A
- Na+/K+ ATase
- Na+/H+ Exchanger
- NKCC
15
Q
- FIltered load of K+
A
Filtered load= GFR x [X]plasma x % filterability
16
Q
- What things are reabsorbed in the proximal tubule?
- What things are excreted into the proximal tubule?
- Major mechanism for reabsorption of K+?
A
- Na+, Cl-, Glucose, Amino Acids, H2O, K+, Bicarb
- H+, Organic acids, bases
- Na+/K+ ATPase of the basolateral membrane
17
Q
- Changing _ reabsorption has considerable effevts on distal tubular _ and _ delivery, which impacts K+ later on
A
- NaCl
- Flow
- Na+
18
Q
- What drives K+ reabsorption in the PT?
A
- Lumen positive transepithelial difference (TEPD)
19
Q
- How does TEPD work in the transepithelial tubule?
A
- In early PT, Na+ is reabsorbed primarily with HCO3-
- Cl- gets left behind
- Negative TEPD builds up
- Cl- is repelled and reabsorbed
- Positive TEPD builds up as Cl- is reabsorbed
- Positive TEPD repels K+
- K+ is reabsorbed paracellularly
20
Q
- How does LOH trabnsport and medullary recycling of K+ occur?
A
- K+ secreted into cortical collecting duct
- K+ is reabsorbed by the outer medullary collecting duct and innner medullary collecting duct
- K+ floats into the interstitium
- K+ is secreted into late Proximal tubule/Descending thin limbs of the LOH
21
Q
Goal of medullary K+ recycling
A
- Increase presence of medullary KC
- Large K+ presence decreases NKCC2 reabsorption by thick ascending limb
- Enhanced Na+ delivery to the distal tubule
- Stimulates Na+ reabsorption and K+ secretion
- Helps you excrete K+ during dietary loading
22
Q
- K+ is secreted or reabsorbed in _ according to the needs of the body
A
- Late distal tubule and cortical collecting duct
23
Q
- What types of cells secrete K+?
A
- Principal cells
- Beta intercalated cells
24
Q
- Most important factors stimulating K+ secretion
A
- Increased ECF [K+]
- Aldosterone
- Increased tubular flow rate
25
Q
- What types of cells reabsorb K+
A
- Alpha intercalated cells
26
Q
- Function of principal cells
A
- Reabsorb: Na+, H2O
- Secrete: K+
27
Q
- Function of alpha intercalated cells
A
- Reabsorb K+ and HCO3-
- Secrete H+
28
Q
- Function of beta intercalated cells
A
- Reabsorb H+ and Cl-
- Secrete K+ and HCO3-
29
Q
- Major factors regulating K+ secretion (buildup of extracellular [K+])
A
- Na+/K+ ATPase activity on basolateral membrane is increased
- Reduced back leakage of K+ from ICF to renal interstitium,
- Increased synthesis of K+ channels and instertion into the luminal membrane
- Increased aldosterone secretion
- Increased distal tubular flow rate
30
Q
- _ is important in helping to preserve normal K+ excretion during changes in Na+ intake and aldosterone levels
A
- Increased tubular flow rate
31
Q
- Define alkalosis
A
- Decrease in H+ ion concentration in the ECF
32
Q
- Define alkalemia
A
- Physiologically high blood pH
33
Q
- Define acidosis
A
- Acute process that increases H+ ion concentration in the ECF
34
Q
- Define acidemia
A
- Physiologically low blood pH
35
Q
- What occurs physiologically during acute alkalosis
A
- Increased activity of the Na+/K+ ATPase pump
- Increased [K+]i
- Increased passive diffusion of K+ into tubule lumen
- Increase in K+ channels
- Increase in K+ secretion
- End result=hypokalemia (k+ is lo)
36
Q
- What occurs physiologically during acute acidosis?
A
- Decreased activity of the Na+/K+ ATPase
- Decreased [K+]i
- Decreased passive diffusion of K+ into tubule lumen
- Decrease in K+ channels on apical membrane?
- Decrease in K+ secretion
- End result=hyperkalemia
37
Q
- What is the key difference between acute v chronic acidosis?
A
- Chronic acidosis stimulates K+ secretion
- Why?
- Chronic metabolic acidosis decreases reabsorption of water and solutes from PCT by inhibiting Na+/K+ ATPase
- Increased tubular flow to DT and CD
- RAAS is stimulated d/t lack of water reabsorption and decrease in ECF volume
- K+ secretion increases
38
Q
- What factors increase K+ secretion
A
ADH
Luminal flow rate
Alkalosis
Glucocorticoids
Anion Delivery
39
Q
- What factors decrease K+ secretion
A
- Acidosis
40
Q
- Diuretics that inhibit Na+ reabsorption willl promote K+ _
A
- secretion
