title: Characterization of human peripheral blood monocyte thromboxane A2 receptors.
abstract: Thromboxane A2 (TxA2) is the predominant eicosanoid metabolite produced by activated human blood-borne monocytes. This study was designed to characterize TxA2 receptors on human peripheral blood monocytes via identification of radioligand binding characteristics using the stable TxA2 mimetic [125I]-BOP ([1S,(1 alpha,2 beta(5Z),3 alpha(1E,3S*),4 alpha]-7-[3-hydroxy-4-(4'- iodophenoxy-1-butenyl)-7-oxabicyclo-[2.2.1]heptan-2-yl]-5-he ptenoic acid) and via analysis of second messenger signal transduction pathways. Scatchard analysis of the binding of [125I]-BOP in human monocyte membranes revealed a single class of binding sites, Kd = 1.49 +/- 0.14 nM and Bmax = 696 +/- 113 fmol/mg membrane protein (n = 8). [125I]-BOP interacted specifically with a TxA2 receptor, as shown by competition binding studies with a range of TxA2 receptor agonists and antagonists that gave a rank order of potency of (-)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid > I-BOP = I-SAP > ONO11113 > SQ29548 > U46619 > (+)-9-chlorobenzyl-6-fluoro-1,2,3,4- tetrahydrocarbazol-1-yl acetic acid. I-BOP caused a dose-dependent increase in intracellular free calcium (EC50 = 7.14 +/- 1.1 nM, n = 4), which was attenuated by preincubation with the TxA2 receptor antagonists SQ29548 (1 microM) and (-)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (100 nM). This study provides further evidence for a TxA2 receptor in monocytes and supports the potential for future characterization of TxA2 receptor subtypes using molecular techniques.
authors.affiliation: Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston.
authors.forename: C J
authors.initials: CJ
authors.lastname: Allan
authors.forename: P V
authors.initials: PV
authors.lastname: Halushka
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic; D000242:Cyclic AMP / Q000096:biosynthesis; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D009000:Monocytes / Q000378:metabolism*; D011869:Radioligand Assay; D017482:Receptors, Thromboxane / Q000378:metabolism*; D015290:Second Messenger Systems; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D017482:Receptors, Thromboxane; C061750:7-(3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo(2.2.1)heptan-2-yl)-5-heptenoic acid; D000242:Cyclic AMP