title: Distribution of binding sites for thromboxane A2 in the mouse kidney.
abstract: Thromboxane A2 (TxA2) is a potent vasoconstrictor eicosanoid that has been implicated in the pathogenesis of both human and experimental renal diseases. The biological actions of TxA2 in the kidney are mediated through specific cell-surface receptors. In this report, we characterize the distribution of thromboxane receptors (TxR) within the normal mouse kidney by receptor autoradiography. With the iodinated TxR agonist [125I]BOP, TxA2 binding sites were detected throughout the kidney. Competitive inhibition curves of whole kidney binding demonstrated a half-maximal inhibitory concentration of 6.5 nM. When Scatchard analysis was performed on anatomically discrete regions, the [125I]BOP binding in the medulla was best fit by a one-site model, with a dissociation constant (Kd) of 8.2 +/- 2.2 nM. In contrast, [125I]BOP binding in the cortex was better described by a two-site model, with estimated Kd of 262 +/- 16 pM for a higher affinity site and 16.9 +/- 1.3 nM for a lower affinity site. These sites do not appear to represent receptor isoforms that arise from alternative splicing of mRNA. The lower affinity binding sites may represent a novel TxR or an alternative affinity state for the previously characterized high-affinity binding site.
authors.affiliation: Department of Medicine, Duke University, Durham, North Carolina, USA.
authors.forename: R B
authors.initials: RB
authors.lastname: Mannon
authors.forename: T M
authors.initials: TM
authors.lastname: Coffman
authors.forename: P J
authors.initials: PJ
authors.lastname: Mannon
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D017482:Receptors, Thromboxane / Q000235:genetics; D013928:Thromboxane A2 / Q000378:metabolism*; D014018:Tissue Distribution; D014158:Transcription, Genetic
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D012333:RNA, Messenger; D017482:Receptors, Thromboxane; C061750:7-(3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo(2.2.1)heptan-2-yl)-5-heptenoic acid; D013928:Thromboxane A2