6-485: Thromboxane B2 ( TXB2 ) is an inactive metabolite/product of thromboxane A2 . It is almost completely cleared in the urine. It itself is not involved in platelet activation and aggregation in case of a wound, but its precursor, thromboxane A2, is. Thromboxane A2 synthesis is the target of the drug aspirin , which inhibits the COX-1 enzyme (the source of thromboxane A2 in platelets). 2-(3,4-Di-hydroxyphenyl)-ethanol (DHPE)
12-438: Is a phenolic component of extra-virgin olive oil . An olive oil fraction containing DHPE can inhibit platelet aggregation and thromboxane B2 formation in vitro. Thromboxane A2 Thromboxane A 2 ( TXA 2 ) is a type of thromboxane that is produced by activated platelets during hemostasis and has prothrombotic properties: it stimulates activation of new platelets as well as increases platelet aggregation. This
18-453: Is a typical G protein-coupled receptor (GPCR) with seven transmembrane segments. In humans, two TP receptor splice variants – TPα and TPβ – have so far been cloned. Thromboxane A 2 (TXA 2 ) is generated from prostaglandin H 2 by thromboxane-A synthase in a metabolic reaction which generates approximately equal amounts of 12-hydroxyheptadecatrienoic acid (12-HHT). Aspirin irreversibly inhibits platelet cyclooxygenase 1 preventing
24-544: Is achieved by activating the thromboxane receptor , which results in platelet-shape change, inside-out activation of integrins , and degranulation . Circulating fibrinogen binds these receptors on adjacent platelets, further strengthening the clot . TXA 2 is also a known vasoconstrictor and is especially important during tissue injury and inflammation. It is also regarded as responsible for Prinzmetal's angina . Receptors that mediate TXA 2 actions are thromboxane A 2 receptors . The human TXA 2 receptor (TP)
30-458: The biologically inactive thromboxane B2 . 12-HHT, while once thought to be an inactive byproduct of TXA 2 synthesis, has recently been shown to have a range of potentially important actions, some of which relate to the actions of TXA 2 (see 12-hydroxyheptadecatrienoic acid ). Due to its very short half life, TXA 2 primarily functions as an autocrine or paracrine mediator in the nearby tissues surrounding its site of production. Most work in
36-451: The formation of prostaglandin H 2 , and therefore TXA 2 . Contrastly, TXA 2 vascular tissue synthesis is stimulated by angiotensin II which promotes cyclooxygenase I's metabolism of arachidonic acid. An angiotensin II dependent pathway also induces hypertension and interacts with TXA 2 receptors. TXA 2 is very unstable in aqueous solution, since it is hydrated within about 30 seconds to
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