Coagulation/ FIbrinolysis Flashcards
List 4 anticoagulant properties of endothelium
- secretion of: (prostacyclin, nitric oxide, heparin sulfate, TFPI, TPA)
- smooth surface
- Protein C receptors = inactivates Va and VIIIa
- Thrombomodulin expression = inactivates thrombin
Prostacyclin function
PLT inhibitor
NOTE: anticoagulant secretion by endothelium
Nitric oxide function
Vascular relaxing (dilation)
NOTE: anticoagulant secretion by endothelium
Heparin sulfate function
anticoagulant secretion by endothelium
TFPI function
Tissue Factor Pathway Inhibitor: suppresses extrinsic pathway
NOTE: anticoagulant secretion by endothelium
Thrombomodulin source + function
- inactivates thrombin
- an anticoagulant secretion by endothelium
Role of WVF in primary hemostasis
Why is vit K needed by coagulation factors ?
What initiates primary hemostasis ?
vascular damage = procoagulant factors released from vessel cells, exposed collagen promotes procoagulants to begin primary hemostasis
List 5 pro-coagulant properties of damaged vasculature
- endothelial cells secrete vWF + up-regulate PLT receptors
- exposed collagen = binds vWF and PLTs
- vasoconstriction (smooth muscles contract)
- PLTs release factors (prostaglandins + prostacyclin)
- smooth muscle contain TF = activates FVII
Describe Adhesion stage of platelet plug
- reversible; PLTs BIND VESSEL WALL
a. MINOR injury = PLTs bind to collagen via GPIa/IIa, GP IV, and GP VI
b. MAJOR injury = PLTs also bind vWFv via GPIb/IX/V receptors before binding wall
Bernard Soulier
GPIb deficiency
- affects adhesion in PLT plug for MAJOR injuries
VonWillebrand Disease
vWF deficiency
- affects adhesion in PLT plug for MAJOR injuries
Describe Aggregation stage of platelet plug
- reversible OR irreversible (TXA2 and ADP)
- PLTs bind other PLTs
- ADP released during PLT adhesion = exposes fibrinogen receptors on PLTs (GPIIb/IIIa integrin) and P-selectin
- PLTs aggregate using fibrinogen and Ca2+
Glanzmann’s Thrombasthenia
GPIIb/IIIa deficiency
- affects aggregation in PLT plug
- reduced fibrinogen receptors on PLTs
Describe Granule Secretion stage of platelet plug
- simultaneously during adhesion/ aggregation
a. ALPHA granules = via SCC system
- PF4
- B thrombomodulin
- PDGF, endothelial GF, Transforming GF
- Factors V, XI, vWF, fibrinogen
b. DENSE = via exocytosis
- ADP/ ATP
- Ca2+, Mg2+
- serotonin
SSC = surface-connected canalicular
Describe Formation/ Function of Thromboxane A2 in a platelet plug
PF3 = PLT phospholipids
- during PLT activation = converted to arachidonic acid = thromboxane A2
- thromboxane A2 = triggers more Ca2+ release = promotes PLT aggregation and vasoconstriction = coagulation
What blocks cyclooxygenase and prevents thromboxane A2 production ?
ASPIRIN leads to impaired PLT function
What is TF and where is it found ?
a transmembrane protein in the endothelium
What are coagulation factors ? Where are they made ?
proteins synthesized by the liver
Define zyomgen
Inactive form of enzymes (coagulation factors)
Define serine protease
enzymes that cleave proteins = must be activated to participate in reaction ie. IIa/ prothrombin
Define cofactor
a substance (other than the substrate) whose presence is essential for the activity of an enzyme
Which coagulation factors are serine proteases ?
Kallikrein
IIa (prothrombin)
VIIa
IXa
Xa
XIa
XIIa
Plasmin
Protein C
Which coagulation factors are cofactors ?
FV and FVIII
Which clotting factors are vit-K dependent ? What is the function of vit K in the synthesis of these factors ?
II/ prothrombin, VII, IX, X (2790) & Protein C/ S/ Z:
- vit K catalyses carboxylation of terminal glutamic acids
- carboxyl group binds Ca2+ = allows binding of PF3
Where are the components of vWF/VIII complex produced ? What are their functions ? What cleaves the complex ?
- vWF = produced by endothelial cells; complexes with VIII = STABLE
- VIII = produced by PLT/ endothelial cells; UNSTABLE by itself
- vWF/VIII is cleaved by thrombin = VIIIa in TENASE complex
Which factors are involved in the extrinsic pathway ?
VII + TF + Ca2+ = TF:VIIa
TF:VIIa + PF3 + X = Xa
INCLUDING factors in COMMON PATHWAY
Which factors are involved in the intrinsic pathway ?
Prekallikrein + HMWK = Kallikrein
Kallikrein + HMWK = XII
XII + collagen = XIIa
XIIa + HMWK + XI = XIa
XIa + Ca2+ + IX = IXa
IXa + (VIIIa + PF3 + Ca2+) + X = Xa
Which factors are involved in the common pathway ?
X + (TENASE complex [intrinsic]/ PF3 AND TF:VIIa complex [extrinsic]) = Xa
Xa + (Va + PF3 + Ca2+) + II/prothrombin = thrombin
Thrombin + fibrinogen = fibrin monomer (soluble)
Thrombin + XIII = XIIIa
XIIIa + Ca2+ +fibrin monomer = fibrin CROSSLINKS (insoluble)
Function of fibrinolytic system
- normally removes fibrin clots that are no longer required
- begins hours after coagulation
- gradual enzymatic cleavage of fibrin = soluble FDPs
Plasminogen: site of synthesis
Liver
Plasminogen: activation
activated by TPA/ Tissue plasminogen activator
Plasminogen: mechanism of action
must be activated into plasmin to cleave fibrin
- promotes fibrinolysis
Plasminogen: target
To cleave FIBRIN in clots and FIBRINOGEN
Function + source of TPA
Tissue Plasminogen Activator:
- secreted by damaged endothelial cells
- promotes fibrinolysis; plasmin to cleave fibrin = FDPs
Activation, function + location of Urokinase
- secreted by kidney
- activated by fibrin and plasmin
- promotes fibrinolysis in renal collecting ducts
Activation, function + location of Plasminogen Activator Inhibitor 1
- secreted by endothelial cells, megakaryocytes, fibroblasts, smooth muscle, monocytes, etc.
- increased in high levels of TPA
- prevents fibrinolysis; inhibits TPA and Urokinase
Function + source of α2-Antiplasmin
- secreted by liver + PLTs
- prevents fibrinolysis; irreversibly binds plasmin
Function, activation and source of TAFI
Thrombin-activatable Fibrinolysis Inhibitor:
- secreted by liver
- activated by thrombin/ thrombomodulin
- prevents fibrinolysis; prevents plasmin formation
What are FDPs ?
Fibrin Degradation Products:
- plasmin cleaves fibrin into characteristic fragments: X, Y, D, E and D-dimers
- plasmin cleaves fibrinogen into X, Y, D, E
- inhibit coagulation cascade
What is the clinical utility of measuring D-dimers ?
- measures fibrinolysis activity
- Detects DIC
Describe TFPI mechanism of action and what factors it inhibits
Tissue Factor Pathway Inhibitor:
- requires Protein S as a cofactor
- inactivates Xa by complexing into TFPI:Xa
- TFPI:FXa binds to TF:VII to prevent further activation of X
Describe the Protein C system; how is it activated ? What does it inhibit ? What is its role in fibirinolysis ?
- activated by thrombin/ thrombomodulin complex
1. Inhibits coagulation = activated Protein C combines with cofactor Protein S = Protein C:S complex inhibits Va and VIIIa
2. Promotes fibrinolysis = forms complex with/ deactivates Plasminogen Activator Inhibitor-1 (PAI-1)
Describe how Antithrombin inhibits coagulation/ which factors it inhibits
- activated by heparin sulfate from endothelial cell surface
- inhibits all serine proteases: Kallikrein, II/ prothrombin, XII, XI, X, IX, plasmin)
What tube/ anticoagulant is used for coagulation testing ?
Sodium citrate
Principle of aPPT test in vitro
In citrated plasma (blue top), the addition of a platelet substitute, factor XII activator, and CaCl2 allows for formation of a stable clot
Is an instrument that uses mechanical end-point detection prone to interference from hemolysis ? Why/ why not ?
How does hemolysis affect coagulation test results, if at all ?
Troubleshooting when QC = 1-3S: First and Second step
How does a high Hct affect coagulation test results ? How can it be corrected ?
How are D-dimers measured on conventional coagulation instruments ?
Immunoassays based on fragment sizes
Factors in TENASE complex. What do they activate ?
VIIIa
PF3
Ca2+
- activates factor X
Which factors are included in the prothrombinase complex ? What do they activate ?
Va + PF3 + Ca2+
- activates prothrombin/II to thrombin
What is PF3 ? What is its role in coagulation ?
PF3 = PLT phospholipids
- during PLT activation = converted to arachidonic acid = thromboxane A2
- thromboxane A2 = triggers more Ca2+ release = promotes coagulation
Differentiate products when plasmin cleaves fibrin vs fibrinogen
Plasmin cleaves Fibrin = X, Y, D, E, D-dimers
Plasmin cleaves Fibrinogen = only X, Y, D, E
Fibrinogen and FDPs by kDa
Fibrinogen > X > Y > D > E
TFPI: Source
- secreted by endothelial cells
- 80% bound to vessel walls
- 20% circulating bound to LDL
How is ZPI activated ? What does it inhibit ?
Protein Z-dependent Protease Inhibitor:
- requires cofactors (protein Z, PF3, Ca2+) to DEGRADE factor X
- by itself, it can inhibit XIa
Glycoprotien IIb/IIIa complex
- A receptor for fibrinogen on the platelet membrane
- It allows PLT binding of fibrinogen and vWF to bind other PLTs
Glycoprotien Ib/IX/V
- A receptor for vWF on the platelet membrane.
- It allows PLT binding of vWF to vascular walls for PLT adhesion.
What do co-factors bind to in the coagulation process?
a.
Fibrinolytic factors to slow down clot digestion
b.
A specific serine protease to increase its activity
c.
Calcium to aid in platelet aggregation
d.
Fibrin monomers to cross-link and stabilize the clot
b.
A specific serine protease to increase its activity
What are the functions of platelets in hemostasis? Select all that apply:
a.
Release of serotonin
b.
Release of prostacyclin
c.
Formation of a hemostatic plug
d.
Activation of the extrinsic coagulation system
a.
Release of serotonin
c.
Formation of a hemostatic plug
Which of the following are functions of thrombin? Select all that apply:
a.
Activates factors V and VIII
b.
Activates anti-thrombin
c.
Activates Factor XIII
d.
Activates factor XI
a.
Activates factors V and VIII
c.
Activates Factor XIII
d.
Activates factor XI
