Thromboxane receptor agonists

A more active thromboxane receptor agonist was found in the 9a-homo-9,l 1-epoxy-5,13-prostadienoic acid analogue, SQ 26,538. This compound was 200 times more potent than arachidonic acid in inducing platelet aggregation but was onl> 1/10 as potent as PGH2. This effect was not blocked by inhibitors of cyclo-oxygenas< or of thromboxane synthetase [241]. 

M. Takasuka, M. Kishi, M. Yamakawa, FTIR spectral study of intramolecular hydrogen bonding in thromboxane A2 receptor agonist (U-46619), prostaglandin (PG)E2, PGD2, PGF2.alpha., prostacyclin receptor agonist (carbacyclin) and their related compounds in dilute carbon tetrachloride solution Structure-activity relationships, J. Med. Chem. 37 (1994) 47. 

III. Short-Term Treatment of Ocular Hypertension A. Thromboxane A2 Receptor Agonists... 

Fluoro prostaglandin, (IV), PGF2a analogs effective as thromboxane A2 receptor agonists were prepared by Klimko (3) and used in the treatment of glaucoma and ocular hypertension. 

Scheurlen M, Kirchner M, Clemens MR, Jaschonek K. Fish oil preparations rich in docosahexaenoic acid modify platelet responsiveness to prostaglandin-endoperoxide/thromboxane A2 172. receptor agonists. Biochem. Pharmacol. 1993 46 245-249. 

Habib A, Vesa R, Crfrninon C, Maciouf J, FitzGerald GA. R id, agonist-dependent phosphorylation in vivo of human thromboxane receptor isoforms. J Biol Chem 1997 272 7191-200... 

M eux PR, Morinelli TA, Williams TC, Hazard ES, Mats DE, Oatis JE, Baron DA, Halushka PV. Differendil effect of pH on thromboxane Aj/prostaglandin Hj receptor agonist and antagonist binding in human platelets. J Biol Chon 1991 266 13752-8... 

Morinelli TA, Oatis Ir. JE, Okwu AK, Mais DE, Mayeux PR, Masuda A, Knapp DR, Hadushka PV. Characterizaticm of an I-labeled thromboxane Aj/prostaglandin Hj receptor agonist J Pharmacol Exp Tlier... 

LEUKOTRIENE RECEPTOR AGONISTS act at receptors recognizing leukotrienes and analogues. The lipoxygenase system forms the leukotrienes, which are members of the eicosanoid family of phospholipid mediators. Their name derives from the fact that leukotrienes are found in leucocytes and contain a triene system of double bonds. The other members of the eicosanoid family are the prostanoids (thromboxanes and the prostaglandins), and these are formed by the cyclooxygenase system see cyclooxygenase INHIBITORS. All the eicosanoids are derived mainly from arachidonic acid. These mediators are synthesized on demand, and in some cases their half-lives are short. The... 

Conversely, proaggregatory agents induce this mechanism of adhesion (e.g. thromboxane. ADP, 5-HT and PAF). 5-HT (serotonin) stimulates platelet aggregation and is. as its name implies, a vasoconstrictor in many blood vessels. It is actively taken up into platelets, and released on insult. See 5-HYDROXYTRYPTAMINE RECEPTOR AGONISTS. 

Finally, the investigational use of new pharmacotherapeutics such as thromboxane synthase inhibitors, vasodilator prostaglandin infusions, antioxidants, and P-receptor agonists in the treatment of microvascular permeability edema is well covered in several reviews (Demling, 1982 McMillan and Boyd, 1982 Persson et al., 1982). 

We observed recently that a relatively high concentration (300 pM) of phthalide 20 in rat PRP significantly inhibited platelet aggregation induced by collagen but not by ADP and U-46619 (a thromboxane A2 receptor agonist) [299]. The inconsistency between the previously reported data and our results may be due to the different species (rat versus rabbit) and preparations (platelet-rich plasma versus washed platelets) used. 

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