BIOL 2420 Lecture Notes - Lecture 7: Tissue Plasminogen Activator, Factor Ix, Coagulation
26 Apr 2018
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Unit 3 – Lecture 7
Anticoagulants Prevent Coagulation
- after coagulation begins
o two mechanisms limit the extent of blood clotting within a vessel
1. inhibition of platelet adhesion
2. inhibition of the coagulation cascade and fibrin production
Table 16.6 – endogenous factors involved in fibrinolysis and anticoagulation
Chemical Factor
Source
Activated by or
Released in
Response to
Role in Anticoagulation
or Fibrinolysis
Other roles and
comments
Plasminogen and
plasmin
Liver and
plasma
tPA and thrombin
Dissolves fibrin and
fibrinogen
N/A
Tissue
plasminogen
activator (tPA)
Many
tissues
Normally present;
levels increase
with stress,
protein C
Activates plasminogen
Recombinant tPA
used clinically to
dissolve clots
Antithrombin III
Liver and
plasma
N/A
Anticoagulant; blocks
factors IX, X, XI, XII,
thrombin, kallikrein
Facilitated by
herparin; no
effect on
thrombin despite
name
Prostacyclin
(prostaglandin I,
or PGI2)
Endothelial
cells
N/A
Blocks platelet
aggregation
Vasodilator
- endothelial cells release anticoagulants (chemicals that prevent coagulation from taking place)
o act by blocking one or more of the reactions in the coagulation cascade
o body produces two anticoagulants
1. heparin
2. antithrombin III
▪ they work together to block active factors IX, X, XI, and XII
o Protein C – another anticoagulant in the body
▪ Inhibits clotting factors V and VIII
- These factors work in controlling coagulation and fibrinolysis, their discovery is important in
developing treatments for many diseases related to coagulation problems
o Example: heart attacks (myocardial infarctions (MIs)
▪ Occur when a coronary blood vessel is blocked by a blood clot
▪ Unless the blockage is removed promptly, the tissue will die or be severely
damaged
▪ Dissolving blood clots
• Can use streptokinase (from bacteria) and tissue plasminogen activator
(tPA)
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Document Summary
Response to tpa and thrombin dissolves fibrin and. Normally present; levels increase with stress, protein c. Anticoagulant; blocks factors ix, x, xi, xii, thrombin, kallikrein. Facilitated by herparin; no effect on thrombin despite name. Anticoagulants prevent coagulation after coagulation begins two mechanisms limit the extent of blood clotting within a vessel inhibition of platelet adhesion inhibition of the coagulation cascade and fibrin production. Table 16. 6 endogenous factors involved in fibrinolysis and anticoagulation. Acetylsalicylic acid (aspirin: an agent that prevents platelet plug formation, acts by inhibiting the cox enzymes that promote synthesis of the platelet activator thromboxane a2. In the human body, the calcium levels do not reach a point low enough to prevent coagulation. Treatment of hemophilia: development of gene therapy for hemophilia b (deficiency in factor ix, patients are injected with a virus engineered to carry the clotting factor ix, and patients begin to synthesize the factor on their own.
