Thromboxanes

• Thromboxanes are eicosanoids derived from arachidonic acid via the COX pathway, specifically from PGH2.
• Thromboxanes play significant roles in hemostasis and vascular function.
• These three groups are collectively called eicosanoids, derived from arachidonic acid via the cyclooxygenase (COX) or lipoxygenase pathways.

Major Thromboxanes:

1. TXA2 (Thromboxane A2):

   • Functions: Promotes platelet aggregation and vasoconstriction, essential for blood clot formation.

2. TXB2 (Thromboxane B2):

   • Function: Inactive metabolite of TXA2, used as a marker for thromboxane production.

Synthesis:

• Platelet Activation: Upon vascular injury, platelets release arachidonic acid.
• COX Pathway: COX-1 in platelets converts arachidonic acid to PGH2.
• Thromboxane Synthase: PGH2 is then converted to TXA2.

Pharmacological Effects:

• Platelet Aggregation: Strongly promote platelet clumping, essential for blood clot formation.
• Vasoconstriction: Cause narrowing of blood vessels, increasing blood pressure.
• Hemostasis: Aid in stopping bleeding by facilitating clot formation at injury sites.

Examples of Thromboxanes:

• TXA₂ (Thromboxane A₂): Potent inducer of platelet aggregation and vasoconstriction.
• TXB₂: Inactive metabolite used as a marker for thromboxane production.

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