title: Endothelial cell-specific ETB receptor knockout: autoradiographic and histological characterisation and crucial role in the clearance of endothelin-1.
abstract: Inactivation of endothelin B receptors (ETB), either through selective pharmacological antagonism or genetic mutation, increases the circulating concentration of endothelin-1 (ET-1), suggesting ETB plays an important role in clearance of this peptide. However, the cellular site of ETB-mediated clearance has not yet been determined. We have used a novel mouse model of endothelial cell-specific knockout (KO) of ETB (EC ETB(-/-)) to evaluate the relative contribution of EC-ETB to the clearance of ET-1. Phenotypic evidence of EC-specific ETB KO was confirmed by immunocytochemistry and autoradiography. Binding of the radiolabelled selective ETB ligand BQ3020 was significantly and selectively decreased in EC-rich tissues of EC ETB(-/-) mice, including the lung, liver, and kidney. By contrast, ETA binding was unaltered. RT-PCR confirmed equal expression of ET-1 in tissue from EC ETB(-/-) mice and controls, despite increased concentration of plasma ET-1 in EC ETB(-/-). Clearance of an intravenous bolus of [(125)I]ET-1 was impaired in EC ETB(-/-) mice. Pretreatment with the selective ETB antagonist A192621 impaired [(125)I]ET-1 clearance in control animals to a similar extent, but did not further impair clearance in EC ETB(-/-) mice. These studies suggest that EC-ETB are largely responsible for the clearance of ET-1 from the circulation.
authors.affiliation: Clinical Pharmacology Unit, Centre for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute, Edinburgh EH16 4TJ, UK.
authors.forename: N F
authors.initials: NF
authors.lastname: Kelland
authors.forename: R E
authors.initials: RE
authors.lastname: Kuc
authors.forename: D L
authors.initials: DL
authors.lastname: McLean
authors.forename: A
authors.initials: A
authors.lastname: Azfer
authors.forename: A J
authors.initials: AJ
authors.lastname: Bagnall
authors.forename: G A
authors.initials: GA
authors.lastname: Gray
authors.forename: F H
authors.initials: FH
authors.lastname: Gulliver-Sloan
authors.forename: J J
authors.initials: JJ
authors.lastname: Maguire
authors.forename: A P
authors.initials: AP
authors.lastname: Davenport
authors.forename: Y V
authors.initials: YV
authors.lastname: Kotelevtsev
authors.forename: D J
authors.initials: DJ
authors.lastname: Webb
mesh_terms: D000825:Animal Structures / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001808:Blood Vessels / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000008:administration & dosage / Q000235:genetics / Q000493:pharmacokinetics*; D004730:Endothelium, Vascular / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics; D006651:Histocytochemistry; D007678:Kidney Glomerulus / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008822:Mice, Transgenic; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D011506:Proteins / Q000235:genetics; D011759:Pyrrolidines / Q000494:pharmacology; D022661:RNA, Untranslated; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics; D044022:Receptor, Endothelin A / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000235:genetics* / Q000378:metabolism; D042787:Receptor, TIE-2; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: C120508:A 192621; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; C110853:Gt(ROSA)26Sor non-coding RNA, mouse; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011506:Proteins; D011759:Pyrrolidines; D022661:RNA, Untranslated; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D020794:Receptor Protein-Tyrosine Kinases; D042787:Receptor, TIE-2; C079086:Tek protein, mouse; D001616:beta-Galactosidase