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Practical work #2. Definition of osmotic resistance of erythrocytes
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Practical work #2. Definition of osmotic resistance of erythrocytes

Resistance of erythrocytes is the ability of erythrocyte membrane to resist the destructive action of low osmotic pressure in solution, where erythrocytes are. In result of such action haemolysis can occur (degradation of the erythrocytes membrane).

Resistance of erythrocyte membrane should be studied relatively to hypotonic solutions of sodium chloride. When concentration is 0,54% - 0,45% normally only erythrocytes with the lowest resistance pass through haemolysis (minimal erythrocytes resistance). In case of further decrease of concentration of sodium chloride more persistent erythrocytes pass through haemolysis. When concentration is 0,40% - 0,34% of sodium chloride even most persistent erythrocytes break down (maximal resistance). Solution becomes transparent, like varnish (as called laky solution). Breach between upper and lower limit of resistance is called amplitude of resistance.

Objectives: to define the borders of changes in osmotic pressure of blood plasma, when the integrity of erythrocyte membrane is kept and estimates the durability of the erythrocyte membrane.

Requirements for work: 7 Vidal’s test-tubes (or plain laboratory tubes), holder, 0,5% solution of sodium chloride, distillated water, blood, conserved with 5% solution of sodium citrate, 3 pipettes with the equal size of the drop openings.

Make following dilutions with 0,5% solution of sodium chloride:

№ of test-tybe

Number of 0,5% NaCl drops

Number of distillated water drops

Concentration of solution

1

25

-

0.5%

2

24

1

0.48%

3

22

3

0.44%

4

20

5

0.40%

5

18

7

0.36%

6

16

9

0.32%

7

14

11

0.28%

Add 1 drop of conserved blood in every test-tube.

Accurately mix the content of every tube until it will get steady color and leave it for 1 hour in a holder.

In 1 hour time observe the destruction of erythrocyte membrane (haemolysis). State of blood is estimated by the grade of color of sodium chloride solution, which is up to sedimentated erythrocytes in test-tubes.

Recommendations for writing down the results:

Write down the value of minimal and maximal erythrocyte resistance.

Calculate its amplitude.

Answer the following questions in conclusion:

Do the borders of changes in osmotic pressure, when erythrocyte membrane keeps its integrity correspond to normal?

Is the integrity of erythrocyte membrane normal?

What testifies increase (or decrease) of the resistance borders?



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