K+
Atomic Number: 19
Electron Configuration:
1s2 2s2 2p6 3s2 3p6 4s1
Never found Free in Nature
Reacts Violently with Water
and Air
KCl used as table salt
substitute and to stop the
Heart (lethal injection)
Used in Fertilizer and Gun
Powder and Glass
manufacturing
K+
History
 1807- Sir Humphry Davy discoveres K
 1871- Salkowski first describes K absorption &
excretion
 1874- Ringer shows that ions balance in natural
salts
 1894- Von Bunge describes relationships
between Na & K
 1926- Miller shows that dietary K is essential for
normal life & Growth
 1966- Woodbury postulates existence of
electrogenic Na-K pump in cell membranes
K+
General Functions
Principle intracellular ion
Intracellular Fluid Regulation:
Osmotically active, involved in buffering, viscosity,
CO2 transport (RBC), & Solublization of proteins
present in the cell
Membrane Effects:
Influences membrane permeability, sodium pump
action, muscular contraction & nerve impulse
conduction
K+
Facts
 Present in all plants and animals
 Alkali metal
– Atomic Wt: 39.1
 Present in the body as K+
– Common inorganic anions:
• Cl, HPO4, bicarbonate, tartate, citrate
– Organic anion:
• Gluconate
 Body Content: 136g/70kg (3000-4000mmol)
 Relative Organ Concentrations:
– RBC > muscle > brain > intestine > heart > pancreas
> liver > kidney > lungs > uterus > skin > adrenal >
skeleton > serum
K+
Facts
 Skeletal Muscle’s mass and K+ concentration
makes total body K+ track closely to lean body
mass
– ~2% total body K+ outside of cells, 98% intracellular
– Intracellular concentration = 140 mmol/L
– Extracellular concentration narrowly maintained @
3.5-5.5 mmol/L
 Important Equation:
E= -61.5 log ([K]
ICF/[K]ECF)
E= membrane potential difference in millivolts
K+
 Important for electrical
properties of membranes
– Hyper or hypo Kalemia can
= failure to depolarize
properly
 Symptoms of Deficiency
& Excess are similar
 Weakness, lethargy, gastric
hypomotility, cardiac
arrhythmias
Facts
K+
Sources
• Food Group K+ mg/100 kcal,
Examples
Leafy Greens 1,300, Spinach, lettuce, cabbage, kale
Fruit of vines 1,200, Tomato, cukes, zucchini, eggplant, pumpkin
Root Veggies
975, Carrots, radishes, turnip, rutabaga, onion
Beans & peas
500, Kidney, green & soy beans; green &
chick peas
Tree fruits
430, Apple,orange,banana,apricot, grapes,
strawberries
Tubers
400, Potatoes, sweet potatoes, yams
Milk & yogurt
350, Skim & whole milk or yogurts
Meats
230, Beef, lamb, pork, poultry, fish, rabbit
Nuts
110, Walnut, cashew, almonds, brazil, fibert
Eggs & Cereal
90, All poultry eggs, wheat, rice, oats, rye
Cheese & pecans 50, Edam, stilton, cheddar, pecans
K+
Influences on Availability
 Decreased:
- Boiling food in water w/ no added salt, addition of
excess NaCl, meat diets, high processed food diets,
diarrhea
 Increased:
- Vegetarian diets, use of salt substitutes
 Typical US diets provide 50-80 mmol K+ per day
 Balance of intake/excretion less percise than Na
& Cl
 Like Na, tolerance to high intakes w/ gradual increase
K+
Absorption & Excretion
Absorption
– K+ well absorbed, >90%
– Absorbed across entire intestinal tract
– Active transport & passive diffusion and/or
facilitation
• Absorption enhanced by Na+, Mg2+, ionophore
• Antagonized by Ca2+, cardiac glycosides &
aldosterone (reverse secretion into gut)
Extracellular Transport
– Free in Blood as K+
K+
Absorption & Excretion
 Excretion
– Half life in blood: ~0.39% of Plasma K+ excreted per
minute at normal plasma levels (1.72 mg/100ml)
• Freely filtered in glomerulus, reabsorbed in proximal tubules,
& secreted in distal tubule via a process facilitated by
aldosterone
• Intestine & bile have little effect on body K+ content in healthy
subjects: 5-10% daily excretion
 Hormones
– Insulin directly stimulates K+ uptake by muscle and
liver
– Aldosterone increases renal excretion
– Catecholamines: beta, hypo K+; alpha, hyper K+
K+
Symptoms
 Deficiency
– Muscle weakness, cardiac arrhythmia, paralysis,
bone fragility, sterility, adrenal hypertrophy, poor
growth, weight loss, death
 Toxicity
– Acute: tonoclonic convulsions, CNS paralysis,
asphyxial convulsions, diarrhea, gastroenteritis,
polydipsia, diuresis, dehydration, renal necrosis,
fever, prostration, dilation of the heart, cardiac
arrhythmia, lung collapse, respiratory failure
– Chronic: cardiac & CNS depression, mental
confusion, weakness, vomiting, numbness, tingling,
flaccid paralysis of extremities
K+
Cellular Transport
 Active Transport = Compartmentalization of K+
–
–
–
–
Na, K – ATPase pump
H,K – ATPase pump
Na-2Cl-K CoTransporters
K conductance channels
 Insulin
– Works to prevent hyperkalemia
 Catecholamines
– Blunt increases in plasma K due to heavy exercise
K+
Deficiency Causes
 Reduced K intake
– Deficient diet or inadequate absorption
 Renal Losses
– Diuretics
– Osmotic diuresis (diabetes)
– Excess mineral corticorticoid
 Intestinal Losses
– Diarrhea
– Laxative abuse
 Redistribution
– Excess Catacholamines or insulin
– Abnormal skeletal muscle calcium channels
K+
Excess Causes
 Excessive Intake
– Decreased renal loss
• Acute renal failure or end stage renal disease
• Mineralcorticoid deficiency
• Potassium-sparing diuretics
 Redistribution
–
–
–
–
Hemolysis, cellular necrosis, muscle injury
Catecholamine antagonists
Insulin deficiency
Abnormal skeletal muscle calcium channels
K+
Hypertension
 Increased K+ diets are hypotensive
– Mechanisms not fully defined
– Evidence based on epidemiology in nature
• Rancho Bernado cohort = 40% ↓ in mortality after 12 yrs w/ ↑
F&V intake
– DASH provided first intervention data
• Whole food so no one nutrient could be tested in isolation
• Complex effect: K+, Mg++, Ca++, & Citrate found in fruits
that is converted to acid buffering bicarbonate in the body
 Blood Pressure appears to be the result of
complex multi-nutrient interactions
– Some effects observed acutely, others are chronic
K+
Bones
K+ now strongly implicated in bone health
– Counteracts Na effects to increase Ca
excretion
– Typically consumed as citrate fruits that buffer
acid load
• Atkins diet = acidotic & calciuric
• Increased kidney stone formation
Marginal K+ Deficiency
– No overt symptoms of hypokalemia
– Insulin resistance occurs
Hi Meat
Lo Fruit & Vegetable
↑Sodium
↑Chloride
↓Potassium
↓HCO3+
↑ H+
↓ Renal
Acidification
Low grade Metabolic acidosis
↑Fluid
Vasoconstriction
↓ Renal Na
Excretion
(gene/age)
↑Urinary
↑Central
Ca++
↓HCO3+
↑ H+
↓Urinary Citrate
↑Kidney Stones
Blood Volume
↑Bone base titration
↑Osteoclastic activation
↓Osteoblastic activation
Essential
Hypertension
Osteoporosis
K+
Recommended Intake
• DRI’s Published
February 2004
Age
0-11m
1-3y
4-8y
9-13y
14-18y
>18y
Wt,
Kg
4.5-8.9
11.0
16.0
25.0
50.0
70.0
400700
1,000
1,400
1,600
2,000
2,000
500700
3,000
3,800
4,500
4,700
4,700
Mg/d
(1989)
Mg/d
(2004)
K+
Fun Facts
Lethal Injection Dosage:
Insulin/K+ uptake –
100mEq KCl
 Insulin binds to recepter = hyperpolarization of cell
membrane = K+ uptake
 Insulin also stimulates Na+ K+ Pump = cellular uptake
of K+
Hyperkalemia Treatment:
 Chronic – Kayexalate (binding resin), Binds K+ in
large intestine, 2-12 hrs
 Acute – treat with insulin, glucose, and Bicarb. =
cellular K+ uptake