Blood plasma

Constitution

Composed to water 91%, the blood plasma contains a large variety of aqueous solutions. Among these aqueous solutions, one finds:

1) mineral aqueous solutions: dissolved trace elements and ions. The total concentration of the ions is a big factor in the maintenance of the osmotic balance of blood. Certain ions also have buffer effect which contributes to maintain the pH of blood between 7,35 and 7,45 at the Human ones. The ions are essential to the exitability of the membranes of the cells and the activity of much of enzymes. (In mmol/l: Na+: 140/Cl: 105/K+: 5/PO4 3: 4/Ca 2+: 2/Mg2+: 1/SO4 2 -: 0,2)

2) respiratory gases (O2, CO2)

3) Organic aqueous solutions. One can distinguish 2 main categories in this class from aqueous solution.

- Substances in transit: the nutrients (lipids, glucids, amino-acids), waste metabolic (urea, uric acid, bilirubine), and hormones.

- Plasmatic proteins (60 to 80 g/l): Together, they have buffer effect which contributes to maintain the pH, to balance the osmotic and oncotic pressure and to confer on blood its viscosity (consistency). The various types of plasmatic proteins also have specific functions.

Plasmatic Proteins

Plasmatic proteins. Plasma would contain 300 different proteins.

The proteins most represented in proportion are the following ones:

Albumin. : + of 50%

Antibody (= Immunoglobulins): 20% (primarily of IgG)

Fibrinogen: 5%

Alpha 1 Antitrypsin: 4%

Alpha 2 macroglobulin: 4% Transferrine: 3%

Lipoproteins (HDL and LDL): 8%

But, even of proteins slightly represented in quantity can have essential functions for the organization. One can distinguish several main categories of functions assumed by plasmatic proteins:

Great functions of plasmatic proteins

The maintenance of the oncotic pressure of the vessels

(water in the vessels maintains)

Albumin, as a majority protein, is essential for this function. In the event of massive hemorrhage or of major burn, the oncotic pressure can thus be restored by the injection of Albumin concentrates.

The transport of molecules

Albumin transports many molecules: Hormones, fatty-acids, bilirubine, Ca 2+, and contains sites of fixing to drugs. This is why any disturbance of the albuminemy involves a Erreur to the measure of the concentration of these molecules. The transferrine transports iron.

The céruloplasmine fixes copper.

The lipoproteins transport the lipids.

Immunizing defense humorale

The immunoglobulins are secreted by the plasmocytes in osseous marrow. They pass then in blood. Three isotypic is present in significant quantities in plasma: IgG” 75%, IgA” 20%, IgM” 5%. The immunoglobulins are fixed at the disease-causing agents. (Virus, bacteria, parasites…) Once fixed, they will allow their elimination in 3 different ways: - The lysis assisted by the Antibodies: certain cells (Natural Killer in particular) have receivers with immunoglobulins. The immunoglobulins thus will connect the disease-causing agent to a cell charged to destroy it. The NK will salt out toxic substances which will perforate the plasmic membrane of its target.

- The opsonisation. The principle is the same one: the Antibody connects an disease-causing agent to a cell. But this time the cell (macrophage for example) will be in measurement of phagocyter (to absorb) the pathogenic one.

- Lysis by the complement. This elimination utilizes another type of plasmatic proteins: proteins of the complement. The complement is activated spontaneously in the presence of a foreign organization. The cells of the body are protected some by inhibiting proteins. In absence of inhibition, the activation of the complement ends up lysing the membranes of the targeted cells. The complement can thus only be activated but the presence of fixed Antibodies will have a role of potentiation.

The blood Coagulation

The implied proteins are the factors of coagulation. These factors are synthesized by the liver. The factors of coagulations will be activated in a " cascade enzymatique" at the time of the lesion of the blood-vessel. The image of cascade is used to popularize the fact that the factors activate the ones after the others. The conclusion of this cascade is the formation of the fibrin clot which will make it possible to stop the hemorrhage.

The fractionation of plasmatic proteins

Many laboratories developed an activity of fractionation of plasma. Fractionation consists in purifying one or more proteins of plasma. The primary goal being to make up innate deficits or asset.

The principal split proteins are:

albumin

It is indicated in the shock hypovolemic (hemorrhage engraves) with hypoalbuminemy. It is also used at the badly burned person or the cirrhotique one (to limit the ascite).

general-purpose immunoglobulins (IgG)

They are indicated at the overdrawn one out of immunoglobulins which would undergo extremely serious infections without the protection of these Antibodies.

They are also used in a great number of pathology car-immunizing. Indeed, in these diseases, the immune system “is put out of order” and attacks the body. The Immunoglobulins resulting from “healthy” donors thus will make it possible “to rebalance” the immune system.

factors of coagulation

The deficits of coagulations are relatively frequent: they are the hemophilia. The hemophiliacs has are most numerous (roughly 2500 in France), they are overdrawn in Factor VIII. Then the hemophiliacs B (approx come. 600 in France) which is overdrawn in Factor IX. There exist also the overdrawn ones in Factor von Willebrand, Factor IX, factor VII in factor XIII.

Concentrates of several Factors (complex pro-thrombiques) are marketed like antidote with the anti-vitamin K: the vitamin K uses the synthesis of many factors of coagulation. Among patients with cardiovascular risks, one limits the risks of formation of clots by anti-vitamin K. In the event of overdose or of serious hemorrhage, it can be vital to quickly restore the presence of the whole of the factors of coagulation. It is thus the indication major of the PPSB.

The fibrinogen and activated factor VII can also be used in the case of serious hemorrhages not controlled at nonoverdrawn subjects.

Sources

Single LFB Biomédicaments French actor of the transformation of plasmatic protein resulting from the blood donations.

Simple: Blood#Plasma

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