title: Response of rat thoracic aortic rings to thromboxane mimetic U-46,619: roles of endothelium-derived relaxing factor and thromboxane A2 release.
abstract: Studies were designed to test the role of the endothelium and endogenous release of thromboxane (Tx) A2 in the contractile response of rat thoracic aortic rings to the TxA2/prostaglandin (PG) H2 mimetic, U-46,619. U-46,619 caused a dose-dependent contraction of rings with endothelium (mean ED50 = 6.54 +/- 3.02 x 10(-9) M; n = 13) which was abolished by the TxA2/PGH2 receptor antagonist, SQ-29,548. Removal of endothelium greatly potentiated (P less than .05) the contractile response to U-46,619 (ED50 = 4.78 +/- 2.14 x 10(-10) M; n = 14). On addition to the organ bath, oxyhemoglobin (10(-6) M), an inhibitor of endothelium-derived relaxing factor, increased vascular smooth muscle contraction in response to U-46,619 and abolished the difference in response between rings with endothelium (ED50 = 6.63 +/- 0.38 x 10(-11) M) and those without (ED50 = 5.13 +/- 0.18 x 10(-11) M). Vascular contraction with U-46,619 (10(-7] was associated with release of immunoreactive TxB2 and 6-keto PGF1 alpha as well as increased conversion of [14C]arachidonate to [14C]TxB2 and 6-keto-[14C]PGF1 alpha. To test the role of endogenous TxA2 in response to U-46,619, the TxA2 synthetase inhibitor UK-38,485 (10(-6) M) was added directly to the organ bath; this diminished (P less than .05) the contractile responses to U-46,619 of rings with and without endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of Florida College of Medicine, Gainesville.
authors.forename: W H
authors.initials: WH
authors.lastname: Folger
authors.forename: D
authors.initials: D
authors.lastname: Lawson
authors.forename: C S
authors.initials: CS
authors.lastname: Wilcox
authors.forename: J L
authors.initials: JL
authors.lastname: Mehta
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013928:Thromboxane A2 / Q000378:metabolism*; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D007093:Imidazoles; D011450:Prostaglandin Endoperoxides, Synthetic; C039242:dazmegrel; D009569:Nitric Oxide; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D013930:Thromboxane-A Synthase