title: Characterization of rat glomerular thromboxane A2 receptors: comparison to rat platelets.
abstract: This study was designed to characterize rat glomerular thromboxane A2 (TxA2) receptors and compare them to rat platelet TxA2 receptors. The radioligand binding characteristics of the receptors were characterized using [125I][1S-(1 alpha,2 beta(5Z),3 alpha-(1E,3R*),4 alpha]-7-[3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo- [2.2.1]heptan-2yl]-5-heptenoic acid ([125I]BOP), a TxA2 agonist. Equilibrium binding with [125I]BOP, as well as competitive binding assays between [125I]BOP and 13-azapinane TxA2 receptors antagonists, were performed in rat glomerular membranes (RGM) and washed rat platelets (WRP). [125I]BOP identified a single class of TxA2 receptor sites in glomerular membranes with a Kd of 318 +/- 55 pM and a Bmax of 260 +/- 62 fmol/mg protein (n = 14). [125I]BOP was displaced by the TxA2 agonist 15S-hydroxy-11 alpha,9 alpha(epoxymethano)-prosta-5Z,13E-dienoic acid (U-46,619) (IC50 = 22 +/- 6 nM, n = 3), the antagonist SQ-29,548 (IC50 = 41 +/- 7 nM, n = 4), and stereoselectively by the antagonists (-)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (L-657,925) (IC50 = 0.27 +/- 0.04 nM, n = 3) and (+)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (L-657,926) (IC50 = 124 +/- 0 nM, n = 2). The ability of six 13-azapinane TxA2 antagonists to compete with [125I]BOP was evaluated. The rank orders for the 13-azapinanes showed no significant correlation between RGM and WRP.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, College of Medicine, University of Florida, Gainesville.
authors.forename: W H
authors.initials: WH
authors.lastname: Folger
authors.forename: P V
authors.initials: PV
authors.lastname: Halushka
authors.forename: C S
authors.initials: CS
authors.lastname: Wilcox
authors.forename: N J
authors.initials: NJ
authors.lastname: Guzman
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001792:Blood Platelets / Q000737:chemistry*; D001643:Bridged Bicyclo Compounds / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D007457:Iodine Radioisotopes; D007678:Kidney Glomerulus / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017482:Receptors, Thromboxane / Q000032:analysis* / Q000187:drug effects; D013931:Thromboxanes / Q000502:physiology*; D014316:Tritium
chemical_list: D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D007295:Inositol Phosphates; D007457:Iodine Radioisotopes; D017482:Receptors, Thromboxane; D013931:Thromboxanes; D014316:Tritium; C061750:7-(3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo(2.2.1)heptan-2-yl)-5-heptenoic acid