Renal Potassium Handling

Hypokalemia, insulin, aldosterone, agonists, alkalemia, hypo

Causes of K+ shifting into cells promotes __kalemia

• Ex: Excess __, __, Beta-2 __ (agonist/antagonist), __emia (base/acid), __smolarity

Hyperkalemia, insulin, antagonists, acidemia, hyper, lysis, exercise

Causes of K+ shifting out of cells promotes __kalemia

• Ex: __ deficiency, __, Beta-2 __ (agonist/antagonist), __emia (base/acid), __osmolarity, cell __, __ (physio state)

Filtered, DCT, collecting duct, secrete, regulation

K+ handling

• K+ is freely __

• More of K+ is reabsorbed in the __ __ __ and __ __, if needed

• Late DCT and collecting duct also __ K+, as needed

  • Primary site of __

Action, graded, Hyper, T waves, ventricular

K+ disturbances

• K+ disturbances affect excitability of __ potentials and __ potentials

• __kalemia Pathology - Peaked _ __ and __ fibrillation

3.5-5.0 (mEq/L)

Normal Extracellular Potassium Concentration =

150 (mEq/L)

Normal Intracellular Potassium Concentration =

Intake, excretion, in cells, extracellular fluid

• External K+ Balance is done between K+ __ and K+ __

• Internal K+ Balance is done between concentrations of K+ __ __ and the __ __

Cells, ECF, ECF, hyperkalemia

Internal K+ Balance

• Relatively small change in K+ exchange between __ and __ may have large impact on __ K+

• High [K+] in ECF = __kalemia

uptake, Na+/K+ ATPase, hyperkalemia

Insulin stimulates K+ __ (into/out) cells

• Insulin stimulates ____ (enzyme)

• Ensures dietary K+ is taken up in cells, to prevent __

Hyperkalemia

In a patient with DM type I, will prolonged period of low insulin levels induce hypokalemia or hyperkalemia?

Into, Beta-2 agonists

Catecholamines Shift K+ __ (into/out) cells

• __ __ __ (hint: ANS drug) - Stimulate Na+/K+ activity

into, out, hyperkalemia

In Acidemia: Blood H+ increase drives H+ __ (into/out) cells

• K+ goes __ (in/out) to blood → __kalemia

out, into, hypokalemia

In Alkalemia: Blood H+ decrease drives H+ __ (into/out) cells

• K+ goes __ (in/out) to cell → __kalemia

ICF to ECF, loses, increases, increases, hyperkalemia

In Hyperosmolarity

• H2O shifts from the __ to __ via osmosis (ICF vs ECF)

• ICF __ (gains/loses) fluid

• __ K+ in the ICF, __ driving force for K+ efflux (increases/decreases) → __kalemia

ECF, ICF, gains, decreases, decreases, hypokalemia

In Hyposmolarity

• H2O shifts from the __ to __ via osmosis (ICF vs ECF)

• ICF __ (gains/loses) fluid

• __ K+ in the ICF, __ driving force for K+ efflux (increases/decreases) → __kalemia

ICF, ECF, trauma, hyperkalemia

In Cell Lysis

• K+ is released from __ to __/blood from a cellular __

• Thus __kalemia

ATP, muscles, blood, hyperkalemia

In Exercise

• Depletion of __ stores and net depolarization

• Open K+ channels in the __ to go to the __

• Thus __kalemia

50-150 (mEq/day)

Dietary K+ intake AND K+ secretion rate are in homeostasis at a range of…

PCT, isosmotic, thick ascending, Na/K/2 Cl, apical, K+, basolateral

External K+ Balance at PCT and Thick ALOH

• 67% of K+ is reabsorbed in the ___

  • Part of __ fluid reabsorption

• 20% of K+ is reabsorbed in the __ __ limb

  • Enters via __ cotransporter on __ membrane

  • Leaves via __ channels on __ and apical membranes

Secretion, principal, basolateral, renal outer medullary K+, apical, reabsorption, alpha, low, apical, K+, basolateral

External K+ Balance at late DCT and Collecting Ducts

• K+__ is done by late DCT and collecting ducts

  • __ cells

  • Enters via Na+/K+-ATPase on __ membrane

  • Leaves via __ __ __ __ channels (ROMK) on __ membrane

• K+ __ in late DCT and collecting ducts

  • __-intercalated cells

  • Occurs when K+ in ECF and tubule is __

  • Enters via H+/K-ATPase on __ membrane

  • Leaves via __ channels on __ membrane

ICF, ECF

Na+/K+ ATPase pump activity is stimulated by high [Na+] in the __ (ICF vs ECF)

OR high [K+] in the __

Principal, electrochemical, ECF, K+ diet, gradient, secretion

• __ cells are primary site of regulating external K+ balance

  • Degree of K+ secretion depends on magnitude of __ gradient across membrane

  • Elevated __ [K+] stimulates Na+/K+-ATPase activity

  • High __ __ → Increase ECF K+ → More K+ enters principal cells → larger __ = more net __ of K+

Na/K, K, Na, increases, ICF, secretion

In principal cells, aldosterone…

• Stimulates synthesis of:

  • a) Basolateral __/__ pumps

  • b) Apical __ and __ channels

• __ Na+/K+ pump activity

• More K+ enters via Na/K pump → Higher K+ in __ (ECF/ICF) is a driving force for K+ __

Na+ reabsorption, K+ excretion

Thiazide and loop diuretics decrease __ __ and increase __ __

(ion reabsorption/ion excretion)

Thiazide diuretics

Inhibit Na+/Cl- symporter at distal convoluted tubule

Loop diuretics

Inhibit NKCC channel at ascending limb of LOH

Lumen, H2O, dilutes, K+ secretion

Net result of Thiazide and Loop diuretics

• More sodium in __ by sodium arrival to collecting ducts

• Inhibit __ (solute) reabsorption

  • __ (action) luminal K+

  • Greater gradient for __ __

Loop

Only these diuretics reduce K+ reabsorption and Na+ reabsorption

K+ sparing

Diuretics harmful to treat patients with hyperkalemia

Aldosterone, K+ secretion, hypo, Na+, K+ secretion

K+ sparing diuretics…

• Either inhibit all actions of __ (i.e. spironolactone)

  • Inhibit __ __, useful for __kalemic patients

• OR Inhibit apical __ channels in principal cells (i.e. amiloride, triamterene)

  • Less Na+ entry → less Na+/K+-ATPase activity → Less __ __

B

Which labs are most consistent with patient with hyperaldosteronism?

A) Low urine K+, high urine Na+  B) High urine K+, low urine Na+

K+ sparing, thiazide/loop

__-__ diuretics are often combined with __/__ (class) diuretics to counteract K+ excretion

H+, K+, Alpha, reabsorption, Beta, secretion

Acid-base disturbances

• Alpha and Beta-intercalated cells directly exchange _+ and _+ via H+/K+-ATPase

• In Acidemia - Greater activation of __-intercalated cells → Increased K+ __

• In Alkalemia - Greater activation of __-intercalated cells → Increased K+ __

Calcium, beta-2/bicarb, insulin, glucose, kayexalate, dialysis and diuretics

Treating hyperkalemia with C BIG K DD….

Calcium

For Tx of Hyperkalemia

• __ Stabilizes cardiac electrical activity, without lowering [K+]

Beta-2 agonists

For Tx of Hyperkalemia

• __ __ stimulate Na+/K+ activity

Insulin, glucose

For Tx of Hyperkalemia

• __ stimulates K+ uptake into cells via Na+/K+-ATPase

• __ given with this to prevent hypoglycemia, without lowering [K+]

Bicarb (HCO3-)

For Tx of Hyperkalemia

• __ raises pH → K+ moves in cells for exchange of H+

Kayexalate

For Tx of Hyperkalemia

__ is a medication that binds K+ in GI tract to prevent dietary absorption of K+

Dialysis and diuretics

For Tx of Hyperkalemia

__ and __ filtering blood to remove excess potassium in blood