Thromboxanes

Thromboxane is a member of the family of lipids known as eicosanoids. The two major thromboxanes are thromboxane A2 and thromboxane B2. The distinguishing feature of thromboxanes is a 6-membered ether-containing ring.

Thromboxane is named for its role in clot formation (thrombosis).

Thromboxane-A synthase, an enzyme found in platelets, converts the arachidonic acid derivative prostaglandin H₂ to thromboxane.

Thromboxane acts by binding to any of the thromboxane receptors, G-protein-coupled receptors coupled to the G protein G_q.

Thromboxane is a vasoconstrictor and a potent hypertensive agent, and it facilitates platelet aggregation.

It is in homeostatic balance in the circulatory system with prostacyclin, a related compound. The mechanism of secretion of thromboxanes from platelets is still unclear. They act in the formation of blood clots and reduce blood flow to the site of a clot.

If the cap of a vulnerable plaque erodes or ruptures, as in MI, platelets stick to the damaged lining of the vessel and to each other within seconds and form a plug. These "Sticky platelets" secrete several chemicals, including thromboxane A2 that stimulate vasoconstriction, reducing blood flow at the site.

Thromboxane A₂ (TXA₂), produced by activated platelets, has prothrombotic properties, stimulating activation of new platelets as well as increasing platelet aggregation.

...
Wikipedia