Thromboxane A2 TxA2 receptor

Recently, it was shown that the thromboxane receptor itself is a substrate ofcGMP-PK and cAMP-PK in HEK293 cells, HEL cells, or with purified enzymes in vitro. Phosphorylation of its cytoplasmic carboxyterminal domain prevented the thromboxane receptor from coupling to and activating G-proteins [36, 37]. For intact platelets, TxA2 receptor phosphorylation has not yet been shown, however, it would provide another explanation for the inhibition of PLC activation and subsequent intracellular Ca2+ elevation and granule secretion in response to cyclic nucleotides. 

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The formation of a platelet aggregate requires the recruitment of additional platelets from the blood stream to the injured vessel wall. This process is executed through a variety of diffusible mediators which act through G-protein-coupled receptors. The main mediators involved in this process are adenosine diphosphate (ADP), thromboxane A2 (TXA2), and thrombin (factor Ila). These mediators of the second phase of platelet activation are formed in different ways. While ADP is secreted from platelets by exocytosis, the release of TXA2 follows its new formation in activated platelets. Thrombin can be formed on the surface of activated platelets (see Fig. 2). 

The prostanoid thromboxane (TP) receptor (TBXA2R) gene has been studied in asthma as a putative candidate gene due to its pharmacology. Thromboxane A2 (TXA2) binds to a specific receptor,... 

While thromboxane A2 (TXA2) and prostaglandin H2 (PGH2) are produced by a large number of mammalian cell types and influence their function, the focus of this review will be primarily on their receptors in vascular smooth muscle and platelets. The potential role of these compounds in mediating physiological and pathophysiological processes in the cardiovascular system and platelets is covered in other chapters of this book. 

The adversary relationship between prostacyclin (PGI2) and thromboxane-A2 (TXA2), which modulates coronary blood vessel caliber [112] and platelet aggregation [113], presents opportunities for therapeutic intervention in cardiovascular diseases. Substances that inhibit TXA2 synthetase or interfere at the TXA2 receptor... 

The characteristics of the four major classes of histamine receptors are summarized. Question marks indicate suggestions from the literature that have not been confirmed. AA, arachidonic acid DAG, diacylglycerol Iko,2+, calcium-activated potassium current IP3, inositol 1,4,5-trisphosphate NHE, sodium-proton exchange, PKC, protein kinase C NO, nitric oxide PTPLC, phosphoinositide-specific phospholipase C TXA2, thromboxane A2. Has brain-penetrating characteristics after systemic administration. 

Fig. (6). Vasoconstrictor mechanism of myricetin. PLA2 phospholipase A2 PL phospholipids AA arachidonic acid COX cyclooxygenase PGG2 prostaglandin G2 PGES prostaglandin endoperoxide synthase PGH2 prostaglandin Hi TXS Thromboxane synthase TXA2 Thromboxane A2 Tp Thromboxane receptor PKC protein kinase C.

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