METABOLISM OF ZINC, MAGNESIUM & ELECTROLYTES

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2.  Metabolism of zinc, magnesium, sodium,
potassium & chloride
› Sources & RDA
› Absorption & excretion
› Biochemical functions
› Disease states
› RGUHS questions
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3.  Zinc is a micro mineral.
 Total body content of zinc: 2 gm.
 Prostate gland is very rich in Zn.
 Zn is mainly an intracellular element.
 60% of zinc is present in skeletal muscle and
30% in bones.
 It is also present in liver, brain & skin.
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4.  Sources:
 Meat, liver, milk, dairy products, legumes,
pulses, nuts, beans & spinach.
 RDA:
 Adults: 15 mg/day.
 Pregnancy & lactation: 15-20 mg/day.
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5.  From duodenum.
 It requires a transport protein – matallo-
thionein.
 Phytates, Ca2+, copper & iron decreases zinc
absorption.
 Small peptides & amino acids promotes zinc
absorption.
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6.  Zinc is component of many metalloenzymes.
› Carbonic anhydrase
› Alkaline phosphatase
› Alcohol dehydrogenase
› Lactate dehydrogenase
› Carboxy-peptidase
› Superoxidase dismutase (cytosol) – anti-oxidant
› DNA and RNA polymerases
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7.  Zn is necessary for
› Storage & secretion of insulin
› To maintain normal levels of vitamin A.
› Synthesis of RBP.
› Proper reproduction, growth & division of cells
› Important element in wound healing.
› Stabilizes protein, nucleic acids & membrane
structure.
› Gusten, a zinc containing protein of the saliva, is
important for taste sensation
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8.  Normal plasma level: 100 mg/dl
 Deficiency:
 Causes:
› Dietary deficiency
› Malabsorption
› Chronic alcoholism
 Symptoms:
› Impaired spermatogenesis
› Growth failure
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9. › Loss of taste sensation
› Impaired wound healing
› Skin lesions such as dermatitis
 Acrodermatitis enteropathica:
 A rare inherited metabolic disease of zinc deficiency.
 Caused by defective absorption of Zn in the intestine.
 Characterized by inflammation around mouth, nose,
fingers, diarrhea & alopecia (loss of hair in discrete
areas)
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10.  Zinc toxicity is rare.
 Seen in welders due to inhalation of zinc oxide fumes
 Clinical features:
› Nausea
› Gastric ulcer
› Pancreatitis
› Diarrhea
› Anemia
› Excessive salivation
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11. Gandham. Rajeev
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12.  Magnesium
› Fourth most abundant cation in the body
› Mainly seen in intracellular fluid
› Second most prevalent intracellular cation
 Body distribution:
 Human body contains 25g of magnesium
 About 60% of which is complexed with
calcium & phosphorous in bones
 30% in soft tissues & 1% is in ECF
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13.  Sources:
› Cereals, beans, vegetables, potatoes, meat, milk,
fruits & fish
 RDA:
› Adult man : 400 mg/day
› Women : 300 mg/day
› During pregnancy & lactation : 450 mg/day
 Absorption:
› Small intestine & excreted in feces
› Calcium, phosphate & alcohol decreases & PTH
increases magnesium absorption.
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14.  Magnesium is required for
› Formation of bones & teeth
› To maintain neuromuscular irritability
 Co-factor:
 More than 300 enzymes requires magnesium as a cofactor
› Hexokinase
› Glucokinase
› Phospho fructokinase
› Pyruvate carboxylase
› Peptidases
› Ribonucleases
› Adenylate cyclase
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15.  Normal plasma levels:
 Serum magnesium: 1.7 - 3 mg/dl
 70% of magnesium exists in free state & 30% is
protein bound (albumin)
 Small amount is complexed with anions like
phosphate & citrate.
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16.  Hypomagnesaemia:
 Decrease in serum magnesium levels <1.7 mg/dl.
 Causes:
› Decreased intake – due to malnutrition
› Decreased absorption – due to malabsorption
› Increased renal loss – due to renal tubular acidosis
 Symptoms:
› Impaired neuromuscular function
› Hypocalcemia – due to decreased PTH secretion
› Tetany, Convulsions & Muscle weakness
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17.  Hypermagnesaemia:
 Increase in serum magnesium > 3.5 mg/dl
 Causes:
 Uncommon but is occasionally seen in renal failure –
decreased excretion
 Excess intake orally or parenterally
 Hyperparathyroidism
 Symptoms:
 Depression of the neuromuscular system, lethargy
 Hypotension, bradycardia
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18. Gandham. Rajeev
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19.  Sodium is the chief electrolyte
› Found in large concentration in ECF
› Total body content of sodium is 4000 mEq or 1.8
gm/kg
› Approximately 50% in bones
› 40% in ECF
› 10% in tissues
› Sodium is found in the body mainly associated
with chlorides as NaCl
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20.  Sources:
› Table salt (NaCl), salty foods, animal foods, milk,
eggs, cereals, carrot, tomato, legumes
 RDA:
 5 gm/day
 Absorption & excretion:
› From GIT – Na+ – K+ pump
› < 2% is normally found in feces & sweat
› In diarrhea, large quantities of sodium is lost in
feces.
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21.  Sodium is essential for
› Maintenance of osmotic pressure & water balance
› It is constituent of buffer & involved in maintenance
of acid-base balance
› It maintains muscle irritability & cell permeability
› Involved in intestinal absorption of glucose,
galactose & amino acids
› Necessary for initiating & maintaining heart beat
 Normal serum sodium: 135-145 mEq/l
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22.  Hyponatremia:
 Decrease in serum sodium level<130 mEq/l
 Causes:
› Vomiting & Diarrhea
› Addison’s disease (adrenal insufficiency)
› Real tubular acidosis (reabsorption is defective)
› Chronic renal failure & nephrotic syndrome
› Congestive cardiac failure
› Edema
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23.  Symptoms of hyponatremia:
› Drop in blood pressure
› Lethergy, Confusion
› Tremors & coma
 Hyponatremia due to water retention:
› Retention of water dilutes the constituents of
extracellular space causing hyponatremia, e.g.
heart failure, liver diseases, nephrotic syndrome,
renal failure, increased ADH secretion.
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24.  Treatment of hyponatremia:
› Administered sodium should be closely monitored
› After sufficient time for distribution -4 to 6 hrs
› Water restriction, increased salt in take
› Anti-ADH drugs
 Sodium loss
› Vomiting, diarrhea, fistula.
› Urinary loses may be due to aldosterone deficiency
(Addison’s disease)
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25.  Hypernatremia:
 Increase in serum sodium concentration > 145 mEq/l
 Causes :
› Cushing’s disease – hyper activity of adrenal cortex
› Prolonged cortisone therapy
› In pregnancy, steroid hormones cause sodium
retention in body
› In dehydration, water is predominantly lost, blood
volume is decreased with increased concentration
of sodium.
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26.  Symptoms:
› Increase in blood volume & blood pressure
› Dry mucous membrane
› Fever
› Thirst
› Restlessness
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27. Gandham. Rajeev
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28.  Potassium is the major intracellular cation.
 Total body potassium is about 3500 mEq.
 About 95% of potassium is in skeletal muscle, 2% is in
ECF.
 Sources:
› Vegetables, fruits, whole grains, meat, milk,
legumes & tender coconut water.
 RDA:
› 3 to 4 gm/day.
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29.  From gastrointestinal tract.
 Excretion:
› Excreted through urine.
 Maintenance of acid-base balance influences K+
excretion.
 Under the normal conditions loss of potassium
through GIT & skin is very small.
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30.  Many functions of potassium & sodium are
carried out in coordination with each other.
 Potassium influences the muscular activity.
 Involved in acid-base balance.
 It has an important role in cardiac function.
 It required for transmission of nerve impulse
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31.  Certain enzymes such as pyruvate kinase
require K+ as cofactor.
 Involved in neuromuscular irritability &
nerve conduction process.
 Potassium is required for proper
biosynthesis of proteins by ribosomes.
 Normal serum potassium: 3.5 to 5 mEq/l.
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32.  Hypokalemia:
 Decrease in plasma potassium concentration
than the normal level.(<3.0 mEq/l)
 Causes:
 Gastrointestinal loss:
 Vomiting, diarrhea or surgical fistula.
 Low potassium diet.
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33.  Renal loss:
› Due to renal diseases.
› Increased aldosterone production.
› Renal tubular acidosis
 Symptoms:
 Muscle cramps, muscular weakness, hypotension,
electrocardiographic changes, tachycardia, lethargy,
cardiac arrest.
 Treatment:
 Supplement adequate potassium
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34.  Hyperkalemia:
 Increase in plasma potassium above the normal
range. (> 5.5 mEq/l)
 Causes:
 Renal failure:
 Kidneys may not be able to excrete potassium.
 Diabetic coma, severe dehydration, intravenous
administration of fluids with excessive potassium
salts.
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35.  Symptoms:
 First manifestation is cardiac arrest (bradycardia
with reduced heart sounds) changes in
electrocardiogram-elevated T wave.
 Treatment:
 Administration of intravenous glucose & insulin –
causes entry of K+ into cells.
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36. Gandham. Rajeev
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37.  Chloride is the major anion in the ECF
 Approximately, 88% of the chloride is found
in the ECF, 12% in the ICF.
 Sources:
 Table salt, leafy vegetables, eggs, milk.
 RDA: 2 to 5 gm/day.
 Absorption:
 From GIT
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38.  Chloride excretion
 Occurs in three ways;
› gastrointestinal tract, skin & urinary tract.
 Chloride is excreted, mostly as sodium
chloride
 Plasma chloride: 96 to 106 mEq/l
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39.  As a part of sodium chloride, chloride is
essential for water balance, regulation of
osmotic pressure & acid-base balance.
 Chloride is necessary for the formation of
HCl in gastric juice.
 It is involved in the chloride shift.
 Salivary amylase is activated by chloride.
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40.  Hypochloremia:
 Decrease in chloride levels is due to
› Excessive vomiting:
› HCL is lost, so plasma chloride is lowered.
› Excessive sweating
› Renal loss occurs in Addison’s disease and salt
losing nephropathy. (renal tubular reabsorption is
decreased)
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41.  An increase in serum chloride level may be due to
› Dehydration,
› Cushing’s syndrome,
› Hyperaldosteronism,
› Severe diarrhea leads to loss of bicarbonate &
compensatory increase in chloride
› Renal tubular acidosis
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42. 1. Biochemical functions of zinc.
2. Biochemical functions of magnesium.
3. Explain the metabolism of sodium,
potassium Chloride
4. Mention the biological reference interval
of sodium, potassium, chloride
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43.  Text book of Biochemistry - U Satyanarayana
 Text book of Biochemistry – DM Vasudevan
 Text book of Biochemistry - MN Chatterjea
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