VASCULAR/PLATELET RESPONSED

• Prostacyclin:

  • Inhibits platelet aggregation
  • Induces vasodilation
• Adenosine:

  • Induces vasodilation
• Thrombomodulin:

  • Inactivates thrombin
  • Enhances anticoagulant activity of protein C
  • Protein C inactivates factor 1 and 7
• Heparan Sulphate:

  • Enhances activity of antithrombin 3
• Tissue plasminogen activity:

  • Converts plasminogen to plasmin
• Von Willebrand factor:

  • Required for platelet adhesion
• 13 Hydroxyoctadecadienoic acid:

  • Inhibits platelet adhesion
• Physiologic Response (VCTF):

  • Vasoconstriction is a neurogenic response
  • Collagen exposure causes adherence of platelets to the site of injury and activates the contact phase of coagulation
  • Tissue thromboplastin release activates the extrinsic pathway
  • Fibrinolysis involves the release of tPA to avoid excessive coagulation
• Platelet Adhesion:

  • Platelets adhere to collagen, fibrinonection, and basement membrane
  • Collagen Type 1 and 2, synthesized by smooth muscle in deep regions of blood vessel walls, promote platelet adhesion, aggregation, and release reaction
  • Platelets adhere to collagen via plasma VIII:vWF and platelets Glycoprotein 1b
• 13 HODE:

  • From endothelial cells
  • Inhibits platelet adhesion
• 12 HETE:

  • From cytosol of platelets
  • Promotes platelet adhesion
• Platelet Release Reaction (Relationship):

  • Release of platelet granules from alpha granules and dense granules
  • Stimulated by collagen, thrombin, epinephrine, and thromboxane A2
• Platelet Shape Change:

  • Contraction of microfilaments due to ADP release
  • Involves calcium and thrombostenin, the major contractile protein