Potassium Imbalance

Disorders of potassium metabolism Yu-Hong Jia, Ph.D Department of pathophysiology Dalian medical university

Potassium function ,[object Object],[object Object],[object Object]

Ⅰ . Normal potassium metabolism

K + Na + ATPase K + H + K + channel 140-160 mmol/L 4.2±0.3mmol/L 50-200mmol/day K + ingestion Kidney colon skin (90%) insulin β-adrenergic agonist ECF [K + ] K + : 50-55mmol/kg B.W toxin (Ba) acid-base state Pump-leak

① free filtration ② reabsorption (90% of filtered potassium) ③ secretion or reabsorption (in normal diet, secretion is major) K + K + K + Proximal tubule &Henle’s loop Distal tubule & Collecting duct

Three elements for achieving potassium secretion: 1. Na + -K + -ATPase on basolateral membrane 2. Permeability of luminal membrane to K+ 3. Electrochemical gradient from blood to tubular lumen ATPase Na + K + K + channel K + Principal cell Basolateral membrane luminal membrane peritubular interstitial tubular lumen K +

factors affecting renal secretion of K + ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],↑ ↑ ↑ K + secretion ↑ K + secretion ↑ K + secretion

K + Na + ATPase K + H + K + channel 140-160 mmol/L 4.2±0.3mmol/L 50-200mmol K + ingestion Kidney colon skin (90%) insulin β-adrenergic agonist ECF [K + ] 50-55mmol/kg B.W ADS ECF K + concentration Urinary flow rate acid-base state toxin drug acid-base state

Ⅱ . Disorders of potassium metabolism

Classification of Disorders of potassium metabolism: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],hypokalemia, hyperkalemia Potassium deficit Hypokalemia, normal serum potassium

Hypokalemia: etiology and pathogenesis (3). ↑K + excretion ,[object Object],[object Object],(1). ↓K + intake (2). ↑K+ shift from ECF to ICF ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Familial hypokalemic periodic paralysis ,[object Object],[object Object],[object Object]

Excessive renal loss of potassium ,[object Object],[object Object],[object Object],[object Object],[object Object],K + H + alkalosis ↑ Urinary flow rate ↓ ECF volume-> secondary ADS increase

Renal tubular acidosis (RTA) ,[object Object],[object Object],[object Object]

Hypokalemia: etiology and pathogenesis (3). ↑K + excretion ,[object Object],[object Object],(1). ↓K + intake (2). ↑K+ shift from ECF to ICF ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Use of certain diuretic agents, Primary and secondary aldosteronism Alkalosis, Renal tubular acidosis, Magnesium deficit

Excessive gastrointestinal loss of K + — vomit, diarrhea, gastric suction ,[object Object],[object Object],[object Object]

Hypokalemia: etiology and pathogenesis (3). ↑K + excretion ,[object Object],[object Object],(1). ↓K + intake (2). ↑K+ shift from ECF to ICF ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Use of certain diuretic agents, Primary and secondary aldosteronism Alkalosis, Renal tubular acidosis, Magnesium deficit Vomit, dirrhea, gastric suction Heavy sweat in hot environment

Hyperkalemia: etiology and pathogenesis (3). ↓ K + excretion ,[object Object],(1). ↑ K + intake (2). ↑K+ shift from ICF to ECF ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Familial hyperkalemia periodic paralysis ,[object Object],[object Object]

2. Alterations of metabolism and function ,[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],Electrical gradient Chemical gradient K + 140-160mmmol/L 4.2±0.3mmol/L Resting membrane potential (RMP) Excitable cell ,[object Object],[object Object],- - - - - + + + + + Na + ATPase RMP ≈ ﹣ 59.5lg Intracellular K + concentration extracellular K + concentration

[object Object],is a wave of depolarization and repolarization that moves across a cell membrane ,[object Object],The critical value of depolarization that can provoke action potential.

hypokalemia ,[object Object],[object Object],[object Object],[object Object],[object Object],hyperkalemia

Irritability (excitability) ,[object Object],[object Object],[object Object],[object Object],[object Object],↑ -> ↓ ↓ ↓ hyperkalemia ↓ ↑ ↑ hypokalemia irritability Difference (between RMP and threshold potential) RMP (negtive value) Neuromuscular cell

hypokalemia ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],hyperkalemia

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],↑ -> ↓ ↓ ↓ hyperkalemia ↑ ↓ ↓ hypokalemia irritability Difference (between RMP and threshold potential) RMP (negtive value) heart

[object Object],[object Object],[object Object],[object Object],↓ ↓ ↓ hyperkalemia ↓ ↓ ↓ hypokalemia conductivity Difference (between RMP and threshold potential) RMP (negtive value) heart

[object Object],[object Object],↓ ↓ hyperkalemia ↑ ↑ hypokalemia contractility Ca 2+ inward flow heart

[object Object],[object Object],[object Object],[object Object],↓ ↓ ↑ hyperkalemia ↑ ↑ ↓ hypokalemia automaticity Net inward current Membrane Permeability to K + heart

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Comparation between action potential and normal electrocardiogram ,[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],ventricles repolarize phase 3 accelerate Peaking of T wave ventricles repolarize phase 3 prolong ventricles repolarize phase 2 inward calcium current accelerate Depressed S-T segment Flattened T wave

hypokalemia ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],hyperkalemia ↓[K + ] ECF H + -K + exchange ↓[H + ] ECF ↑[H + ] ICF ↑Renal excretion of H + aciduria K + shift out of cells H + shift into cells alkalosis (Paradoxical aciduria) ↑[K + ] ECF H + -K + exchange ↑[H + ] ECF ↓[H + ] ICF ↓Renal excretion of H + Alkaline urine K + shift into cells H + shift out of cells acidosis (Paradoxical alkaline urine)

hypokalemia ,[object Object],[object Object],[object Object]

Potassium Imbalance

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