tromboxane

Thromboxane is a group of potent biologically active lipids that act as signaling molecules. They are derived from fatty acids, primarily arachidonic acid. The most well-known thromboxanes are thromboxane A2 (TXA2) and thromboxane B2 (TXB2). TXA2 is synthesized in platelets and is involved in various physiological processes, most notably blood clotting and vasoconstriction.

In platelets, arachidonic acid is converted to prostaglandin H2 (PGH2) by the enzyme cyclooxygenase (COX). PGH2 is then acted upon by thromboxane synthase to produce TXA2. TXA2 is a short-lived molecule that binds to specific receptors on platelets and vascular smooth muscle cells.

The effects of TXA2 are multifaceted. It promotes platelet aggregation, which is crucial for hemostasis, the process of stopping bleeding. It also causes vasoconstriction, narrowing of blood vessels, which can increase blood pressure. These actions are important in wound healing but can also contribute to pathological conditions such as thrombosis and atherosclerosis if dysregulated.

TXA2 is rapidly hydrolyzed to the inactive metabolite TXB2, which is then cleared from the body. The balance between TXA2 production and its inactivation is tightly regulated. Medications that inhibit cyclooxygenase, such as aspirin, are widely used to reduce TXA2 synthesis and thereby prevent blood clots. Drugs that block TXA2 receptors are also used in cardiovascular therapy.

---