The proteins in the plasma are:

1. Serum albumins

2. Serum globulins and

3. Fibrinogen.

When the blood is shed out of the blood vessel or collected in a container, the coagulation occurs. In this process, the fibrinogen is converted into fibrin and the blood cells are attached to this fibrin forming the blood clot. After about 45 minutes, a straw colored fluid leaves blood clot. This fluid is called serum. The serum is different from plasma in its protein content. The serum contains only the albumins and globulins. The fibrinogen is absent in serum because, it is converted into fibrin during the coagulation of the blood. Serum contains all the other constituents of plasma except fibrinogen.

Thus, the Serum = Plasma - Fibrinogen. Because of this, the albumins and globulins are usually called serum albumins and serum globulins.

NORMAL VALUES

The normal values of the plasma proteins are:

Total proteins : 60-80 g/l

Serum albumins : 35-50 g/l,

Serum globulins : 23-35 g/l

Alpha1 - : 1-4 g/l

Alpha2 - : 4-12 g/l

Beta- : 5-11 g/l

Gamma- : 5-16 g/l

Fibrinogen : 2-4 g/l

PROPERTIES OF PLASMA PROTEINS

The following are the properties of plasma proteins.

1. MOLECULAR WEIGHT

The molecular weight of albumin : 69,000

The molecular weight of globulin: 156,000

The molecular weight of fibrinogen: 4,00,000

Thus, the molecular weight of fibrinogen is greater than that of other two proteins.

2. ONCOTIC PRESSURE

The plasma proteins are responsible for the oncotic or osmotic pressure in the blood. The osmotic pressure exerted by proteins in the plasma is called colloidal osmotic pressure. Oncotic pressure represents osmotic pressure part and depends on proteins content in solution. Although proteins concentration is rather big in a solution, molecules general amount is relatively low due to their big molecular weight. That is why oncotic pressure is not more than 25-30 mm Hg. Albumins play a major role in exerting oncotic pressure. The share of their contribution to oncotic pressure determining is 80%. It is so because of their low molecular weight and molecules big amount in plasma.

Oncotic pressure plays important role in watery exchange regulation. The bigger is oncotic pressure, the more water is maintained in vascular bed and the less is transported into the tissues and on the contrary. Oncotic pressure not only influences on tissular liquid and lymph formation but also regulates uroformation and water absorbtion in intestine.

Hypoproteinemy observed at proteinic fasting as well as kidneys hard pathological conditions leads to edemas because water can not be maintained in vascular bed and comes to the tissues.

3. SPECIFIC GRAVITY

The specific gravity of the plasma proteins is 1,026.

4. BUFFER ACTION

The acceptance of hydrogen ions is called buffer action. At birth acidosis is physiologic. Ph is supported by: buffer systems, excretory organs and lungs.

Buffer systems:

· bicarbonate,

· phosphate,

· protein,

· hemoglobin (75 per cent of all system).

The plasma proteins have 1/6 of total buffering action of the blood.

ORIGIN OF PLASMA PROTEINS

IN EMBRYO

In embryonic stage, the plasma proteins are synthesized by the mesenchyme cells. In embryo, the albumins are synthesized first and other proteins are synthesized later.

IN ADULTS

In adults, the plasma proteins are synthesized mostly from reticuloendothelial cells of liver. The plasma proteins are also synthesized from spleen, bone marrow and disintegrating blood cells and general tissue cells. Gamma globulin is synthesized from B-lymphocytes.

FUNCTIONS OF PLASMA PROTEINS

The plasma proteins are very essential for the body. The following are the various functions of the plasma proteins

1. ROLE IN COAGULATION OF BLOOD

Fibrinogen is essential for the coagulation of blood. During coagulation of blood, the fibrinogen is converted into fibrin.

2. ROLE IN DEFENSE MECHANISM OF BODY

The gamma globulins play an important role in the defense mechanism of the body by acting as antibodies (immune substances). These protein are also called immunoglobulins. The antibodies react with antigens of various microorganisms, which cause diseases like diphtheria, typhoid, streptococcal infections, mumps, influenza, measles, hepatitis, rubella, poliomyelitis, etc.

3. ROLE IN TRANSPORT MECHANISM

Plasma proteins are essential for the transport of various substances in the blood. Albumin, alpha globulin and beta globulin are responsible for the transport of the hormones, enzymes and respiratory gases, particularly carbon dioxide. The alpha and beta globulins play an important role in the transport of metals in the blood.

4. ROLE IN MAINTENANCE OF ONCOTIC PRESSURE IN BLOOD

Because of their large size, the plasma proteins cannot pass through the capillary membrane easily and remain in the blood. In the blood these proteins exert the colloidal oncotic pressure. The oncotic pressure exerted by the plasma proteins is about 25 mm Hg. In this way, the plasma proteins play an important role in the maintenance of oncotic pressure of blood.

Since the concentration of albumins is more than the other plasma proteins, it exerts maximum pressure, globulins are the next and fibrinogen exerts least pressure.

Importance of Oncotic Pressure - Starling's Hypothesis

Oncotic pressure exerted by the plasma proteins is involved in the exchange of various substances between blood and the cells through capillary membrane. According to Starling's hypothesis, the net filtration through capillary membrane is proportional to the hydrostatic pressure difference across the membrane minus the oncotic pressure difference.

5. ROLE IN REGULATION OF ACID-BASE BALANCE

Plasma proteins, particularly the albumins, play an important role in regulating the acid- base balance in the blood. This is because of the virtue of their buffering action

6. ROLE IN VISCOSITY OR INTERNAL FRICTION OF BLOOD

It is often determined comparatively to water viscosity: if the latest one is equal to 1, blood viscosity is equal to 4,0-5,0. In new-borned - 10,0-14,0; in 1 month – like in the adult. In girls this index is less than in boys. Main reasons for viscosity increasing:

· in mountains;

· hypercapnia (carbonic acid content increasing in blood);

· inflammations;

· hypertony;

· atherosclerosis;

· at feeding of mainly animal food (proteins-rich) – meat, eggs.

Main reasons for viscosity decreasing:

· at vegeteranian feeding.

Viscosity depends on formed elements (mainly erythrocytes) amount and proteins concentration. The plasma proteins provide viscosity to the blood, which is important to maintain the blood pressure. Albumin provides maximum viscosity than the other plasma proteins.

7. ROLE IN ERYTHROCYTE SEDIMENTATION RATE (ESR) EITHER BLOOD SUSPENSIONAL STABILITY OR VELOCITY SEDIMENTATION RATE (VSR).

Blood represents suspension from physical-chemical point of view because formed elements are in plasma in a suspended state. Suspension is a liquid containing other substance particles that are distributed equally. Erythrocytes suspension in plasma is sustained by their surface hydrophilic nature as well as their negative membrane surface charge that they possess like other formed elements. Thus, erythrocytes are pushed away one from another. If formed elements negative charge is reduced that can be connected with positive proteins of cathions adsorbtion than favorable conditions are created for erythrocytes mutual gluing. Such a gluing is especially powerful at fibrinogen and gamma-globulins adsorbtion on their membrane. Mentioned proteins form so-called bridges between separate erythrocytes due to which their aggregation occurs and so-called coin columns are formed. Real power of aggregation represents difference between force in formed bridges, force of negatively charged red blood cells electrostatic pushing away and shift power causing aggregates decomposition. It is not excluded that proteins molecules connection at the erythrocytes surface takes place due to weak hydrogenic bonds as well as dispersal forces of Van-der-Waals.

If erythrocytes aggregation is observed in organism than blood viscosity is increased that can create favorable conditions for blood intravascular coagulation as well as blood pressure increasing. Moreover, “coin columns” prevent cells, tissues and organs normal blood supply at their sludging in capillaries.

If one puts blood in the test-tube after preliminary adding substances preventing coagulation than one can see after some time that plasma was divided into two layers: the superior one consists mainly of plasma and the inferior one – of formed elements. Taking into account mentioned features Ferreus proposed to study erythrocytes suspension stability while their sedimentation determining in blood the coagulation of which is liquidated by preliminary adding of citric sodium. Nowadays this reaction is known as erythrocytes sedimentation velocity or rate (ESR). Other name is velocity sedimentation rate (VSR). This method is rather simple in usage, non-specific (gives information at many physiological and pathological conditions) and that is why is still judiciously used in theoretical and practical medicine all over the world.

Normal VSR is determined by plasma normal proteinogram. This index depends on age and sex. It is equal to 6-12 mm/h in adult men, 8-15 mm/h in adult women, 15-20 mm/h in the old of both sexes, 1-2 mm/h in babies (it reaches adult values up to sexual maturation period). The biggest contribution to VSR has highly-molecular protein fibrinogen. Women have bigger fibrinogen level than men (it is physiological facility to prevent regular menstrual bleedings and bleedings during labors). That is why VSR can reach even 15-20 mm/h at menstruations and 20-30 mm/h during pregnancy.

Erythrocytes concentration and proteins (especially highly-molecular ones) content are two distinguishing factors that determine VSR level. So, if erythrocytes number is little (anemia) than the resting number of them are easily to be sedimentated than to their normal or increased number in one and the same volume. Thus, anemia is accompanied by increased VSR, erythrocytosis (red blood cells increased number) – decreased VSR.

Inflammatory, infection diseases are accompanied by proteins content increasing in blood (immunoglobulins at infection, acute-phased proteins at inflammation) especially of highly-molecular ones. It leads to VSR rising. Tumors (especially cancerogenous) are connected with very-highly molecular proteins production which are absorbed on cells (erythrocytes in part). As the scientists concluded, VSR rising from 40 and upper can testify to tumors or temporal arteriitis (this disease should be excluded). VSR equal to 100 mm/h is a cancer distinguishing feature. Burnings and combustions are accompanied by tissular proteins enforced decomposition (catabolism) and, thus, hyperproteinemy, that leads to VSR rising. Other pathological conditions the VSR increasing at which is a diagnostic criterium are as follows as: myocardial infarction, post-operative period, hemoblastoses (myelomic disease at which Bens-Jons' protein causes occlusion in vessels in kidney capillaries in part that can lead to kidney insufficiency and death; Waldenstrem's disease, disease of immunoglobulins hard chains at which lymphocyte anomalous precursor produce only hard chains of lg that lead to their level rising in blood and thus enforced absorbtion onto erythrocytes external membrane), chronic active hepatitis (as a result of hyperglobulinemy), liver cirrhosis, tuberculosis, amyloidosis, collagenoses (tissues proteins catabolism).

VSR reducing is observed at erythremy and symptomatic erythrocytoses (erythrocyte number increasing), viral hepatitis (hypoglobulinemy result), mechanic jaundice, different hypoproteinemies, salicylates and calcium chloride taking. VSR decreasing lower than 3 mm/l is unfavorable diagnostic sign because it testifies to blood viscosity increasing.

VSR level depends more on plasma features in bigger extent than on erythrocytes ones. So, if to put male erythrocytes with normal VSR in a pregnant woman plasma than they will begin their sedimentation with the same velocity like female erythrocytes during pregnancy.

8. ROLE AS RESERVE PROTEINS

During the conditions like fasting, inadequate food intake or inadequate protein intake, the plasma proteins are utilized by the body tissues. Because of this, the plasma proteins are called the reserve proteins.

Shortly,

Albumins – (60 % or 35-50 g/l) produced in liver; are agile, low-weighted, they are important for:

· oncotic pressure support;

· bilirubin transport;

· hard metals salts transport;

· fat acids transport;

· medicines transport (proteins increase action periods for them).

Globulins (40% or 30-35 g/l) are formed in liver, bone marrow, spleen. Role:

· form antibodies;

· antitoxins;

· agglutinines;

· blood coagulation (some of them are clotting factors);

· phospholipid transport;

· cholesterol transport;

· steroid hormones transport;

· oncotic pressure support (less than albumins);

· blood density support;

· buffers;

· blood viscosity determination;

· nutritive function.

VARIATIONS IN PLASMA PROTEIN LEVEL

The level of plasma proteins vary independently of one another. However, in several conditions, the quantity of albumin and globulin change in opposite direction.

DECREASE IN ALL FRACTIONS OF PROTEINS–HYPOPROTEINEMIA

Hypoproteinemia occurs in the following conditions:

1. Hemorrhage

2. Extensive burns

3. Pregnancy

4. Malnutrition

5. Prolonged starvation

6. Cirrhosis of liver and

7. Chronic infections like chronic hepatitis or chronic nephritis.

INCREASE IN ALL FRACTIONS

HYPERPROTEINEMIA

Hyperproteinemia occurs in the following conditions: