Dr. Maliyah (HEMOSTASIS-Block 1.2 -MM

8/3/2019 Dr. Maliyah (HEMOSTASIS-Block 1.2 -MM

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HEMOSTASISBLOCK 1.2.

MALIYAH MADIYAN, dr, S.U.

DEPARTMENT OF BIOCHEMISTRYFAC. OF MEDICINE

GADJAH MADA UNIVERSITY


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TOPIC

I. BIOMEDICAL IMPORTANCE

II. HEMOSTASIS

III. THROMBOSIS IV. BLOOD COAGULATION PROCESS

V. ANTICOAGULANT

VI. BLEEDING DISORDERVII. FIBRINOLYSIS BY PLASMIN


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I. BIOMEDICAL IMPORTANCE

Hemorrhagic & thrombotic statescause

serious medical emergencies : e.g.

- thromboses in coronary arteries & }

cerebral arteries }

causes death in many parts of the world. Rational management of these conditions require the bases of blood clotting &

fibrinolysis.


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II. HEMOSTASIS

IS THE CESSATION OF BLEEDING FROM ACUT/SEVERED VESSELS

INVOLVES : blood vessels, platelets

aggregation, plasma proteins Initially vasoconstriction of the injured

vessel diminished blood flow distal to

injury. hemostasis & thrombosis share 3

phases.


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Conted (1). formation of a loose & temporary

platelets aggregate at the site of injury. a. platelets bind collagen (at the site of

vessel wall injury) release ADP+ form

thromboxane2 activate other platelets b. thrombin formed during coagulation

further platelets activation platelets

change shape. c. In the presence of fibrinogen, aggregate form hemostatic plug (in hemostasis) or

thrombus (in thrombosis).


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Conted

(2). Formation of fibrin mesh bindsplatelet aggreagate hemostaticplug/thrombus more stable

(3). Partial/complete dissolution ofthe hemostatic plug/ thrombus byplasmin.


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III. THROMBOSIS

Occurs : if the endothelium lining blood vessels isdamaged or removed (eg. rupture of an athero-sclerotic plaque).

Types of thrombi : (1).White thrombus : platelets + fibrin, poor red

cells. at the site of an injury/abnormal vessel wall,

particularly in areas where blood flow is rapid(arteries).

(2).Red thrombus : red cells + fibrin. at the areas with retarded blood flow /stasis

(eg.veins) (3). Disseminated Fibrin deposit : in a very small

blood vessels or capillaries.


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Blood clotting Factors: Table 50-1

I = fibrinogen VIII = Antihemophilic factor A,II= Prothrombin Antihemophilic globulin (AHG)III= Tissue factor IX = Antihemophilic factor B,IV = Ca++ Christmas factor, Pasma throm-V= Proaccelerin, boplastin component (PTC)

Labile factor, Ac X= Stuart Prower factor(accelerator) globulin XI = Plasma Thromboplastin-VII = Proconvertin Antecedent (PTA)Cothromboplastin, XII = Hagemann Factor

SPCA (serum prothrombin XIII = Fibrin stabilizingConversion accelerator) factor (FSF), Fibrinoligase.


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Functions of Coagulation factorsTable : 50-2.

1. Zymogen of serine protease(inactive):

XII, XI, IX, VII, X, II

2. Cofactors :

VIII, V, III

3. Fibrinogen : I

4. Thiol dependent transglutaminase :XIII

5. Regulatory & other proteins :

Protein C, Protein S, Thrombomodulin


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IV. BLOOD COAGULATION PROCESS

Fig. 50-1

Intrinsic pathway

XII converts toXIIa by PK & HK XIIa activates XI toXIa ( + Ca++ & HK)

XIa activates IX to IXa (+ Ca++ )

IXa activates X toXa (+ Ca++ & PL +VIIIa)


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II. BLOOD COAGULATION PROCESS (Conted)

Extrinsic pathway: VII, III, X, Ca++ (IV)

VII VIIa by Xa (positive feedbackhypothesized)

VIIa + tissue factor (III) activate XXa.[VIIa + III = tissue factor complex]

TFPI (Tissue Factor Pathway Inhibitor):

Protein circulates in the blood associated withlipoproteins.TFPI directly inhibits Xa (binds theenzyme near its active site).

Extrinsic to intrinsic activation :

VIIa + III

activate IX

IXa


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II. BLOOD COAGULATION PROCESSConted

Final Common pathway : (intrinsic &extrinsic):

Xa activates II IIa (+ Ca++ & PL +

Va). IIa activates I (fibrinogen) fibrin

monomer (Ia) fibrin polymer

IIa activates XIII (transglutaminase) XIIIa (+ Ca++ ).

XIIIa (fibrinoligase) catalyzes fibrinpolymer into cross-linked fibrin polymer.


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II. BLOOD COAGULATION PROCESSConted

Thrombin (IIa) function, activates: 1. IIa

2. V Va

3. VIII VIIIa 4. XI XIa (hypothezied)

5. XIII XIIIa.


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Tenase & prothrombinasecomplex

Tenase complex : IV (Ca++) & VIIIa

Prothrombinase complex :IV, Va, Xa & II

Assembly of these complex : on themembrane surface of platelets activated

to expose the phosphatidylserin(phospholipid) { normally on the internal sideof the plasma membrane of inactivatedplatelets (thrombocytes)

See fig. 50-2


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Intrinsic pathway:

More important in fibrinolysis than incoagulation because :

1. kallikrein, XIIa, XIa can cleave

plasminogen into plasmin. 2. kallikrein can activate single chain

urokinase (anticoagulant).

3. hereditary deficiency of XII, XI,kallikrein, HK do not exhibit bleedingproblem.


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V. ANTICOAGULANT1. NaF (sodium fluoride) invitro

2. Oxalate in vitro3. Citrate in vitro4. EDTA (Ethylene diamine tetra acetate) invitro5. Thrombine inhibitor : (physiologically)

Antithrombine (75%) inhibit :IXa, Xa, XIa, XIIa, tissue factor complex. 2 macroglobulin ) most of the remainder of

antithrombin activity.

1 antitrypsin ) minor inhibitor Heparin cofactor II )6. Coumarine inhibit vitamin K- Dependent

carboxylation of factors II, VII, IX, X.


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Coumarine (eg. Warfarin)

Inhibits : carboxylation of Glu Gla (-

carboxy glutamate) in amino terminalregion of factors II, VII, IX, X and protein

C & S (sythesized in liver) : Fig.44-8(page 496): Harpers ed.27.


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Control of thrombine

1. feed back mechanisms: thrombin whichis produced inhibits the activation ofprothrombine

2. inhibitor of thrombine in the blood


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VI. Bleeding Disorder

1). VIII deficient Hemophilia A (X-

chromosome linked disease)

2). IX deficient Hemophilia B

3). Vitamin K deficient.


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VII. FIBRINOLYSIS BY PLASMIN

Fibrinolysis = the process to disolve the fibrin clotsby plasmin (synthesized inactive plasminogen)

Plasminogen activator

NH3+-------------Arg

Val --------------COO-

S S plasminogen

NH3+-------------Arg Val --------------COO-

S S plasmin

2 chains of plasmin held together by disulfide bond.

= serine residu of the active side


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Plasminogen activator

1). t-PA (tissue plasminogen activator):serine protease from vascular endothelium selective, only degrades fibrin clots

widely used in thrombosis therapy(eg.coronary thrombosis).

2). urokinase (isolated from urine)synthezied by monocytes, macrophage,fibroblast & epithelial cells.

3). streptokinase less selective than t-PA,can degrade fibrinogen in circulation and

plasminogen that is bound in fibrin clots


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Plaminogen inhibitor

1). Plaminogen activator inhibitor

inhibits tPA

2). 2-antiplasmin inhibits plasmin

(Fig.50-7)


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Memo

1. study the original reference.

2. study fig. 50-1 -----> 50-8

3. study yourself : plateles activation(Fig.50-8).References :

Harpers Illustrated Biochemistry 27th Ed. ByMurray et. al., 2006.

THANK YOU FOR YOUR ATTENTION

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Dr. Maliyah (HEMOSTASIS-Block 1.2 -MM