Presentation describes about the Major extra- and intra-cellular electrolytes of human body and their physiological roles. In next part, it discuss the Electrolytes used in replacement therapy, ORS and Physiological acid-base balance.

1. MAJOR EXTRA- AND INTRA-CELLULAR
ELECTROLYTES
By
Dr. Nidhi Gupta
Assistant Professor
M.M. College of Pharmacy
M.M. (Deemed to be University), Mullana, Ambala, Haryana

2. TABLE OF CONTENT
 Introduction
 Role of Major Physiological Cations and Anions
 Electrolytes used in replacement therapy
 Oral rehydration salts (ORS)
 Physiological acid base balance

3. INTRODUCTION
 Electrolytes are the minerals present in the body consists of
inorganic ions which can be either cationic or anionic in character.
 Examples: Anionic Electrolytes: HCO3
-, Cl-, SO4
2-
, HPO4
2-.
Cationic Electrolytes: Na, K, Ca and Mg
 The electrolyte conc. of body fluids is different in various fluid
compartments including intracellular, interstitial and plasma.
 It is the conc. of dissolved ions in each compartment that creates
the osmotic pressure for holding the water in appropriate space.

5.  The conc. of some important electrolytes in intra-cellular, extra-cellular
and plasma are given in below mentioned table 1:
 Table 1: Concentration of Important Electrolytes
Ions Extracellular
electrolytes (mEq/L)
Intracellular
electrolytes
(mEq/L)
Plasma
(mEq/L)
Cations
Na+ 142 10 135-145
K+ 4 140 4.5-5.5
Ca++ 2.4 0.0001 2.1-2.6
Mg++ 1.2 58 1.5-3.0
Anions
Cl- 103 4 98-105
SO4
2- 1 2 0.3-1.5
HCO3- 28 10 25-31
PO4
2- 4 75 1.2-3.0

6. ROLE OF MAJOR PHYSIOLOGICAL CATIONS AND ANIONS
 Mineral salts in the body are required for carrying out all the body processes.
 They are needed in small quantities.
 Mainly required elements are calcium, phosphorus, iron, sodium, potassium
and chloride.
 General functions of Electrolytes are:
1. To control osmosis of water between different body compartments
2. Maintainence of acid-base balance required for normal cellular activities.
3. Generation of action potential and controlled secretion of some hormones
and neurotransmitters.

7. SODIUM
 It is the most abundant extracellular ion and constitutes around 90% of
extracellular cations.
 Normal plasma sodium concentration: 136 to 142 m Eq/litre.
 Normal intake of sodium per day: 5 to 20 g.
 Daily requirement: 3 to 5 g.
 Excess quantity is excreted in urine.
 Important physiological role:
1. It is the main component of extracellular fluid associated with chloride and
bicarbonate in controlling the acid-base equilibrium.
2. It is required in preserving the normal irritability of muscles and permeability
of cell.

8. 3. Transmission of nerve impulses in nerve fibers.
4. Maintenance of osmotic pressure of various body fluids and protecting
the body against excessive fluid loss.
 Conditions of Hyponatremia (low serum sodium level):
a) Excessive sodium excretion in ‘metabolic acidosis’.
b) Excessive urination in case of ‘diabetes inspidus’.
c) Diarrhea and vomiting.
d) Decrease excretion of hormone aldosterone.
o Conditions of hypernatremia (high serum sodium level):
a) Severe dehydration
b) Hyper adrenalism
c) Certain type of brain damage
d) Excessive treatment with sodium salt

9. POTASSIUM
o It is most abundant cation in intracellular fluid.
o Normal plasma concentration: 3.8 to 5.0 mEq/litre.
o Normal intake of potassium per day: 5 to 7g.
o Daily requirement: 1.5 to 4.5 g.
o The good source of potassium in food including milk, certain
vegetables, meat and whole grains.
o Important physiological roles:
1. Contraction of muscle, especially cardiac muscle.
2. Transmission of nerve impulses.
3. Maintain the electrolyte composition of various body fluid.
4. Biochemical activities inside the cell.

10.  Conditions of hypokalemia (low serum potassium level)
a) Malnutrition
b) Gastrointestinal losses
c) Diarrhea
d) Used of diuretic like acetazolamide and chlorothazide is able to increase
the excretion of potassium in urine.
e) In heart diseases
Conditions of hyperkalemia (high serum potassium level)
a) Patients suffered from renal failure
b) Advanced dehydration or shock
c) Addison’s disease.

11. CALCIUM
 Total calcium content in body: 22 g/kgbody wt.
 Daily requirement: 0.8 g
 Mostly found in bones and remaining largely found in extra-cellular
fluid.
 Main dietary source is milk, cheese, green vegetable, eggs.
 Calcium absorbed from all parts of small intestine by an active
transport mechanism.
 Normal range for total plasma calcium: 2.2 to 2.6 m mol/lit.
Important physiological roles:
1. Functioning of nerves and muscles.
2. It is associated with vitamin D and phosphorus in hardening of
bones.

12. 3. It is involved in blood coagulation and muscle contraction.
4. It is needed for the release of acetylcholine from the preganglionic
nerve terminals.
 Calcium ion level in plasma is regulated by parathyroid hormone and
calcitonin.
 Intestinal absorption gets reduced in conditions like vitamin D
deficiency, kidney failure and in intestinal malabsorption.

13. MAGNESIUM
 It is the second most common intra cellular electrolyte and fourth most
abundant cation in body.
 Normal human body have 25 g of Magnesium (54% being present in bone
along with phosphorus, 45% in intra cellular fluid and 1% in extra cellular
fluid).
 3.3 to 4.9µ mol of Mg excreted through urine
 Daily requirement: 350 mg.
 Dietary source: nuts, soyabeans, whole grains and sea foods.
 Absorption mainly from duodenum.
Important Physiological Roles:
1. Magnesium ions activate enzymes involved in carbohydrate and protein
metabolism.
2. Important in myocardial function, neural transmission and neuromuscular
activity.
3. Also needed for the operation of Na+-K+-ATPase pump system.

14.  Conditions for Hypomagnesemia:
 1. Malabsorption.
 2. Diarrhoea
 3. Chronic alcoholism.
 Conditions for Hypermagnesemia:
 1. Addison’s disease
 2. Acute diabetic acidosis.
 3. Severe dehydration.
 4. Hypothermia or renal failure.

15. CHLORIDE
 It is major anion of all body fluids.
 Normal body range: 50 m Eq per kg body wt.
 Daily body requirement: 5 to 10 gm as sodium chloride.
 Dietary source is common table salt which is use in cooking.
 Excretion is mainly through urine and skin during sweating.
 Pharmacological function:
a) Maintain osmotic pressure between different body fluids.
b) Maintain the charge balance between body fluid.
c) Formation of gastric hydrochloric acid
d) Maintenance of acid-base balance

16.  Conditions for Hypocholremic alkalosis:
 In normal physiological conditions, no deficiency of chloride ion takes
place, in case of more utilization, deficiency takes placewhich causes
vomiting.

17. PHOSPHATE
 Phosphate ions are the main anions of intracellular fluid.
 Normal plasma phosphate concentration: 1.7 to 2.6 mEq/litre.
 Dietary source: Milk, milk products, whole grains, legumes and nuts.
 Maximum phosphate present in the cells as phospholipids, ATP or with
nucleic acids.
 Important roles:
1. Buffering systems of body.
2. Erythrocyte-glucose metabolism.
 Phosphate deficiency takes place in patients with a calcium deficiency.
Phosphate depletions occurs as a result of renal tubular disorders or in
patients consuming large amounts of antacids particularly, aluminium
hydroxide.

18. SULPHATE
 It is present in very small quantities in plasma and interstitial fluid.
 Dietary sources: Animal and Plant proteins having Sulphur containing
amino acids such as cysteine and methionine.
 Roles:
 Sulphur containing compounds are used in detoxication mechanism
whereas –SH containing compounds are used in tissue respiration.

19. BICARBONATE
 It is the second largest anion in the extra-cellular fluid compartment.
 It is used as important buffer system in maintaining the acid-base
balance along with carbonic acid.
 Lack of bicarbonate make the blood pH less than 7.25 and excess
causes metabolic alkalosis.

20. ELECTROLYTES USED IN REPLACEMENT THERAPY
 Under the normal conditions, body adjust the electrolyte balance and
no replacement become necessary. In various conditions such as
prolonged fever, severe vomiting or diarrhoea, there occurs heavy
loss of water and electrolytes. To compensate this, administration of
lost electrolytes in appropriate concentration of tonocity becomes
essential.
 Two types of electrolyte solutions are used in replacement therapy.
A) A solution for rapid initial replacement
B) A solution for subsequent replacement

21. SODIUM CHLORIDE
 Formula: NaCl and Mol. Wt. : 58.45
 It is having not less than 99% and not more than the equivalent of
100.5% of NaCl with reference to the substance dried at 1300 C.
 Preparation: In laboratory it is prepared from common salt in water
by passing hydrochloric acid gas. Crystals are precipitated out.
 Properties:
1) It occurs in the white or colourless powder
2) It is odourless and having saline taste.
3) Soluble in water and insoluble in alcohol.

22.  Test for purity: It has to be tested for acidity and alkalinity, As, Ba, Ca
and Mg, Fe and heavy metals bromide, iodide, sulphate.
 Loss on drying: It should not be more than 1.0% . It is determine on
1g by drying in an oven at 130o C.
 Storage: It is store in tightly closed containers in dry place as it
absorbs moisture.
 Uses:
1. It is a source of both sodium and chloride ions.
2. Dosage forms are solutions, tablets and parentral solutions. 0.9%
w/v solutions is isotonic and used as wet dressing and irrigating body
cavities or tissues.
3. Sodium chloride eye lotion (B.P): 0.85 to 0.95% w/v of NaCl.
4. Sodium chloride solution (B.P) 0.9% w/v NaCl in purified water.
5. Sodium chloride injection: sterile isotonic solution of NaCl in water
for injection. It contains not less than 0.85% w/v and not more than
0.95% w/v of NaCl. Contains no antimicrobial agents.

23. POTASSIUM CHLORIDE
 Formula: KCl and Mol. Wt. : 74.55
 It is having not less than 99.3% of KCl which is calculated with
reference to the substance dried to constant weight at 105o for two
hours.
 Properties:
1) It occur as colorless prismatic or cubical crystal or as a white
granular powder.
2) Salt is odorless and saline taste.
3) It is soluble in water and insoluble in alcohol and solvent ether.
4) It melts at 7720 C

24.  Test for purity: It is tested for acidity or alkalinity, As, Bs, Ca, Mg, Fe,
heavy metal, bromide, iodide, sulphate and loss on drying.
 Uses:
1) It is used as an electrolyte replenisher.
2) It is also used when hypolkalemia or hypochloremic alkalosis exists
as has been the case after prolonged diarrhea or vomiting.
3) It is some time used as diuretics.
4) This salt is most widely used for oral replacement of potassium in the
form of solution.
5) It find use as adjunct in treatment of myasthenia gravis(severe
muscle weakness).

25. ORAL REHYDRATION SALTS (ORS)
 A large number of formulations are available in the market which
contain anhydrous glucose, sodium chloride, potassium chloride and
either sodium bicarbonate or sodium citrate.
 These dry powder preparations to be mixed in a specific amount of
water and are used for oral rehydration therapy.
 These preparations contain a flavouring agent and a suitable agent for
free flow of powder.

26. TABLE 2: FORMULATIONS FOR ORS
Ingredient Formula I Formula II Formula III
Sodium chloride 1.0 gm 3.5 gm 3.5 gm
Potassium chloride 1.5 gm 1.5 gm 1.5 gm
Sodium bicarbonate 1.5 gm 2.5 gm -
Sodium citrate - - 2.9 gm
Anhydrous glucose 36.4 gm 20 gm 20 gm
Glucose 40 gm 22 gm -
Above three formulations are usually prepared. The quantities given are for preparing 1 litre
solution.
THE FORMULA II AND III ARE RECOMMENDED BY WHO AND UNICEF FOR CONTROL IN
DIARRHOEL DISEASES

27. PHYSIOLOGICAL ACID BASE BALANCE
 Body fluids have balanced quantities of acid and base. They should be well
balanced.
 The maintenance of normal range within the body has been essential
because the biochemical reaction taking place in the living system are very
sensitive to even small changes in acidity or alkalinity.
 The pH values of certain body fluids are given in table 3:
Table 3: pH of body fluids
Sr. no. Body fluids pH range
1 Urine 4.5-8.0
2 Blood 7.4-7.5
3 Gastric juice 1.5-3.5
4 Saliva 5.4-7.5
5 Bile 6.0-8.5
6 Semen 7.2-7.6

28. ACIDOSIS AND ALKALOSIS
 pH of blood of a healthy person is constant around 7.35.
 If pH becomes low, acidosis results.
 If pH level is high, alkalosis results.
 Even the strong acids and bases are continually taken into and
formed by the body, pH of the fluid inside and outside the cells
remains constant due to the presence of buffer system.
 Buffer systems are only effective when there is a mechanism by which
excess acid or alkali can be excreted out of the body which is best
done by lungs and kidneys.
 Electrolytes play a vital role in regulating the body’s acid-base
balance. It is maintained by controlling the H+ conc. of body fluids.

29.  In healthy adults, extra-cellular fluid pH range is between 7.35-7.45
and the normal H+ conc. in body fluids is only 40mEq/litre.
 Most of the metabolic reactions takes place within a very narrow pH
range, controlling the H+ conc. is essential for survival and is done by
below mentioned mechanisms:
 1. Buffer system
 2. Elimination of some ions through urine by kidney.
 3. Through the respiratory centre.

30. 1. BUFFER SYSTEMS
 Buffer system consist of weak acid and its salts.
 Buffer helps to restrict the changes in the pH of body fluids by
converting strong acid and base into weak acids and base.
 Buffers are able to remove the excess H+ from the body fluids but not
from the body.
 Buffer system exists in the body fluids are follows;-
I. Carbonic acid-bicarbonate buffer system
II. Phosphate buffer system
III. Protein (hemoglobin) buffer system

31.  2. Elimination of some ions through urine by kidney-
 Absorption of certain ions and elimination of others are able to control
the acid base balance of blood and thus the body fluids.
 3. Through the respiratory centre –
 Change in rate of breathing is able to control the removal of CO2
from
body fluid which gives rise to changes in pH of blood carbonic acid.