Biomaterial Database

Photoaffinity receptor antagonist for human platelet thromboxane A2/prostaglandin H2 receptors. 1990

D E Mais, and N Liel, and P V Halushka

Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston 29425.

9,11-Dimethylmethano -11,12-methano-16-(3-azido-4-iodophenoxy)-13,14- dihydro-13-aza-15 alpha beta-omega-tetranor TXA2 (I-PTA-PON3) was synthesized and evaluated as a potential photoaffinity probe of the human platelet thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor. I-PTA-PON3 inhibited the aggregation of washed human platelets induced by the TXA2 mimetic U46619 [(15S)-hydroxy-11 alpha, 9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid]. Schild analysis of the data revealed a Kd of 9.5 nM and a slope not significantly different from -1. Equilibrium binding studies using [125I]PTA-OH, a TXA2/PGH2 receptor antagonist, showed that I-PTA-PON3 plus photolysis resulted in a 52% reduction in the number of binding sites (1252 +/- 202/platelet) compared to the nonphotolyzed group (2557 +/- 293/platelet) (N = 5, P less than 0.05) with no significant change in the Kd. Repetition of the incubation with I-PTA-PON3 and photolysis a second time resulted in a further 77% (578 +/- 163 binding sites/platelet) reduction in the number of binding sites. Incubation of washed human platelets with I-PTA-PON3 (163 nM) followed by photolysis and removal of the non-covalently bound I-PTA-PON3 resulted in no change in the EC50 value for the TXA2 mimetic, U46619, when compared to controls that were either exposed to I-PTA-PON3 and not photolyzed or exposed only to photolysis. The second photolysis of I-PTA-PON3 resulted in a significant 42% increase in the EC50 value of U46619-induced aggregation compared to the non-photolyzed group (N = 4, P less than 0.05). These results suggest that I-PTA-PON3 is a useful probe for the study of TXA2/PGH2 receptors and that spare TXA2/PGH2 receptors may exist in the platelet.

UI	MeSH Term	Description	Entries
D010782	Photolysis	Chemical bond cleavage reactions resulting from absorption of radiant energy.	Photodegradation
D010974	Platelet Aggregation	The attachment of PLATELETS to one another. This clumping together can be induced by a number of agents (e.g., THROMBIN; COLLAGEN) and is part of the mechanism leading to the formation of a THROMBUS.	Aggregation, Platelet
D011450	Prostaglandin Endoperoxides, Synthetic	Synthetic compounds that are analogs of the naturally occurring prostaglandin endoperoxides and that mimic their pharmacologic and physiologic activities. They are usually more stable than the naturally occurring compounds.	Prostaglandin Endoperoxide Analogs,Prostaglandin Endoperoxide Analogues,Synthetic Prostaglandin Endoperoxides,Analogues, Prostaglandin Endoperoxide,Endoperoxide Analogues, Prostaglandin,Endoperoxides, Synthetic Prostaglandin
D011463	Prostaglandins H	A group of physiologically active prostaglandin endoperoxides. They are precursors in the biosynthesis of prostaglandins and thromboxanes. The most frequently encountered member of this group is the prostaglandin H2.
D011982	Receptors, Prostaglandin	Cell surface receptors that bind prostaglandins with high affinity and trigger intracellular changes which influence the behavior of cells. Prostaglandin receptor subtypes have been tentatively named according to their relative affinities for the endogenous prostaglandins. They include those which prefer prostaglandin D2 (DP receptors), prostaglandin E2 (EP1, EP2, and EP3 receptors), prostaglandin F2-alpha (FP receptors), and prostacyclin (IP receptors).	Prostaglandin Receptors,Prostaglandin Receptor,Receptor, Prostaglandin,Receptors, Prostaglandins,Prostaglandins Receptors
D001792	Blood Platelets	Non-nucleated disk-shaped cells formed in the megakaryocyte and found in the blood of all mammals. They are mainly involved in blood coagulation.	Platelets,Thrombocytes,Blood Platelet,Platelet,Platelet, Blood,Platelets, Blood,Thrombocyte
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000345	Affinity Labels	Analogs of those substrates or compounds which bind naturally at the active sites of proteins, enzymes, antibodies, steroids, or physiological receptors. These analogs form a stable covalent bond at the binding site, thereby acting as inhibitors of the proteins or steroids.	Affinity Labeling Reagents,Labeling Reagents, Affinity,Labels, Affinity,Reagents, Affinity Labeling
D001386	Azides	Organic or inorganic compounds that contain the -N3 group.	Azide
D013928	Thromboxane A2	An unstable intermediate between the prostaglandin endoperoxides and thromboxane B2. The compound has a bicyclic oxaneoxetane structure. It is a potent inducer of platelet aggregation and causes vasoconstriction. It is the principal component of rabbit aorta contracting substance (RCS).	Rabbit Aorta Contracting Substance,A2, Thromboxane