FIBRIN

From Big Medical Encyclopedia

FIBRYN (Latin fibra fiber) — the water-insoluble protein which is formed of fibrinogen at effect of thrombin on it in the course of a blood coagulation. The blood fibrinous clot stopping bleeding consists of the threads F weaved into dense network. and the uniform elements of blood captured by them.

T. it is formed of the fibrinogen dissolved in a blood plasma (see) at effect of proteolytic enzyme of thrombin (see).

Biol. role F. consists in implementation of a hemostasis (see), protection of wound surfaces against contagiums by formation of a fibrinous barrier; T. participates also in a reparation of connecting fabric and in inflammatory processes (see the Inflammation). Disturbance of a fibrinoobrazovaniye or qualitative inferiority F. lead to frustration of a hemostasis, to emergence of gems of an orraga cheska of diathesis (see).

Transformation of fibrinogen in F. occurs at disturbance of integrity of blood vessels or at p and tolite. in N at t r is wasps at d is that m with in e r t y in and - scientific research institute of blood (perhaps, in a blood channel there is a continuous education F.). This process includes three stages. In the first stage thrombin causes eliminating from fibrinogen of a fibrinoiyeptid And (a pier. the weight of 2000), then a fibrinoiyeptida In (a pier. weight of 2400). The rest of a molecule of fibrinogen carries the name fibrin-monomer. In the second stage there is spontaneous polymerization fibrin-monomers in fibrin-polymers, the last have an appearance of proteinaceous threads, in to-rykh a molecule fibrin-monomers are connected by the hydrogen bindings formed between the remains of amino acids of tyrosine (see) and a histidine (see). Polymerization (see) it is carried out gradually through formation of dimer, Trim ditch etc. This stage occurs without participation of thrombin and, according to V. A. Belitser's theory and sotr., the program of self-assembly fibrin-monomers by the specific functional centers is its cornerstone. At the same time there is a change of a form of molecules F. from globular in fibrillar. In process of formation of bunches of protofibrils cross striation of molecules F forms.

In the third stage under the influence of the enzyme called by fibrinsta-biliziruyushchy, or XIII blood-coagulation factors in the presence of ions of Sa2g there is a binding fibrin-polymers covalent bonds. The factor of XIII causes reaction of transfer of amide group with formation of a peptide bond between the rest of a glutamine of one molecule of protein and the rest of a lysine another. Reactions of the third stage cause stabilization of protein, or cross-linking action between polymers F., also lead to education in fibrin at first dimer of 7 chains, and then polymers and-tseiyey. Stabilization improves haemo static properties of fibrin as a result of increase in mechanical strength and elasticity of a clot F., reduction of its sensitivity to proteolysis and increases in a role in a reparation of fabrics. Optimum temperature for polymerization F. temperature is 37 ° at pH from 6,9 to 7,4. Acidulation of solution to pH 5,1 — 5,3 breaks polimerizatsiyug at increase in a pH value to 5,7 — 6,1 there is spontaneous polymerization. Shifts of pH towards neutral or alkalescent reaction promote formation of a fibrinous clot. Speed of education F. it is more or less constant at 30 — 40 °. At temperature increase to 50 ° fibrin is not formed owing to an irreversible denaturation of fibrinogen. Except thrombin, education F. cause proteases of snake poisons (see) — reptilaza, are wines (ankrod), defibraza and dr: At the same time defective fibrin since proteases of snake poisons chip off from a molecule of fibrinogen only peptide A or peptide B is formed and do not activate a factor of XIII.

Molecule F. just as fibrinogen consists of three types of the polipep-tidny chains designated and, | 3 and at and the fibrinopeptides A and B differing from it in absence in and - and (3 chains. A formula stabilized F. represent as (are, (3, u2) where the are designates polymers and - chains, u2 — dimeasures at - chains. T. let's not dissolve in salt solutions, in alkalis and to-takh.

The fibrinous clot which is formed under natural conditions at a blood coagulation includes blood serum and uniform elements, it has ability to adsorb on the surface and to inactivate significant amounts of thrombin and X фактора^ blood coagulations. T., received from 1 mg of fibrinogen, adsorbs up to 2000 PIECES of thrombin. In this regard F. it is designated as antithrombin I.

Clots F. are exposed to retraction and a lysis. Proteolytic splitting F. is caused by a number of proteases, including the trypsin (see) splitting up to 360 bonds in a molecule F. Specific for F. the iro-teaza (see) splits fibrinolysin in its molecule to 160 — 180 peptide bonds therefore the main are formed four a cleavage product — fragments of X, Y, D and E; from them only the fragment

of D is characteristic of the stabilized fibrin, to-ry unlike a fragment of the D fibrinogen the dimeasure, containing covalently connected at - chains has the form.

T. in fabrics and bodies find by methods of a submicroscopy and coloring by eosine and Mallori's hematoxylin (see Mallori methods) and across Veygert (see Veygert methods of coloring). T. in a blood plasma determine by Rutberg's method. At the same time add to 1 ml of a blood plasma 0,1 ml of 5% of solution of calcium chloride, the formed clot F. take and dry on filter paper to a so-called sukhovozdushny state, then weigh.

In a wedge, practice drugs F. use in the form of a fibrinny sponge or a film (see Fibripnaya a sponge, a film) for healing of wounds and a stop of bleeding (see).

Bibliograndreenko G. V. Fibrinolysis. (Biochemistry, physiology, pathology), M., 1979; Belits of V. A ER.

Domains — large functionally important blocks of molecules of fibrinogen of N of fibrin, in book: Biochemistry of animals and the person, under the editorship of M. D. Kursky, century 6, page 38, Kiev, 1982; 3 at and and r about in D. M. Biot

chemistry of a blood coagulation, M., 1978; Kudryashov B. A. Biological problems of regulation of liquid state of blood and its coagulation, M., 1975; Human blood coagulation, haemostasis and thrombosis, ed. by B. Biggs, Oxford a. o., 1972;

Per-1 i with k E. Gerinnungslaboratorium in Kli-nik und Praxis, Lpz., 1971. See also bibliogr. to St. Coagulant system of blood.

G. V. Andreenko.

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