title: Differential actions of the prostacyclin analogues treprostinil and iloprost and the selexipag metabolite, MRE-269 (ACT-333679) in rat small pulmonary arteries and veins.
abstract: The prostacyclin (IP) receptor agonists, treprostinil, iloprost and the selexipag metabolite, MRE-269 (ACT-333679) were evaluated in rat distal pulmonary blood vessels. Small pulmonary arteries and veins were pre-contracted with the thromboxane mimetic, U46619 (25 and 100nM, respectively), and relaxation determined with and without IP receptor antagonists, RO1138452 and RO3244794. In arteries, treprostinil was a more potent vasorelaxant than iloprost, while the efficacy of iloprost was greater. In pulmonary arteries, treprostinil-induced relaxation was essentially abolished by both IP antagonists (1μM), while responses to iloprost were partially inhibited. Both treprostinil and iloprost were equipotent, prominently relaxing pulmonary veins with responses being similarly and partially sensitive to IP antagonists. In contrast, RO1138452 failed to inhibit relaxations to MRE-269 in either pulmonary arteries or veins, suggesting no involvement of typical IP receptors. Thus, rat pulmonary tissues cannot be considered appropriate to assess classical IP receptors using the proposed highly selective non-prostanoid agonist MRE-269, contrasting with the IP receptor agonism profile of prostacyclin analogues, iloprost and treprostinil.
authors.affiliation: Division of Medicine, University College London, London, UK; Research and Education, Aspetar - Qatar Orthopaedic and Sports Medicine Hospital, P.O Box 29222, Doha, Qatar.
authors.forename: N N
authors.initials: NN
authors.lastname: Orie
authors.forename: A
authors.initials: A
authors.lastname: Ledwozyw
authors.forename: D J
authors.initials: DJ
authors.lastname: Williams
authors.forename: B J
authors.initials: BJ
authors.lastname: Whittle
authors.forename: L H
authors.initials: LH
authors.lastname: Clapp
mesh_terms: D000081:Acetamides / Q000378:metabolism*; D000085:Acetates / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D001572:Benzofurans / Q000494:pharmacology; D001593:Benzyl Compounds / Q000494:pharmacology; D011464:Epoprostenol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D016285:Iloprost / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D011422:Propionates / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects* / Q000502:physiology; D011667:Pulmonary Veins / Q000187:drug effects* / Q000502:physiology; D011719:Pyrazines / Q000378:metabolism* / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044006:Receptors, Epoprostenol / Q000037:antagonists & inhibitors; D014664:Vasodilation / Q000187:drug effects
chemical_list: C514222:(2-(4-(4-isopropoxybenzyl)-phenylamino) imidazoline); D000081:Acetamides; D000085:Acetates; D001572:Benzofurans; D001593:Benzyl Compounds; D007093:Imidazoles; D011422:Propionates; D011719:Pyrazines; C515593:RO3244794; D044006:Receptors, Epoprostenol; C523468:selexipag; D011464:Epoprostenol; C531934:(4-((5,6-diphenylpyrazin-2-yl)(isopropyl)amino)butoxy)acetic acid; D016285:Iloprost; C427248:treprostinil
keywords: IP receptor agonists; Iloprost; MRE-269; Prostacyclin analogues; Prostanoid IP receptors; Rat distal pulmonary arteries; Treprostinil