title: Melatonin inhibits nitrate tolerance in isolated coronary arteries.
abstract: (1) The present study was designed to test the hypothesis that melatonin inhibits nitrate tolerance in coronary arteries. (2) Rings of porcine coronary arteries were suspended in organ chambers for isometric tension recording. Nitrate tolerance was induced by incubating the tissues with nitroglycerin (10(-4) M) for 90 min, followed by repeated rinsing for 1 h. Control rings that had not been exposed previously to nitroglycerin, but were otherwise treated identically, were studied simultaneously. The rings were contracted with U46619 (1-3 x 10(-9) M) and concentration-response curves to nitroglycerin (10(-9)-10(-4) M) were obtained. (3) Nitrate tolerance was evident by a 15- to 20-fold rightward shift in the concentration-response curve to nitroglycerin in rings with and without endothelium exposed previously to the drug for 90 min. Addition of melatonin (10(-9)-10(-7) M) to the organ chamber during the 90-min incubation period with nitroglycerin partially inhibited nitrate tolerance in coronary arteries with intact endothelium; however, melatonin had no effect on nitrate tolerance in coronary arteries without endothelium. (4) The effect of melatonin on nitrate tolerance in coronary arteries with endothelium was abolished by the melatonin receptor antagonist, S20928 (10(-6) M). In contrast to melatonin, the selective MT(3)-melatonin receptor agonist, 5-MCA-NAT (10(-8)-10(-7) M), had no effect on nitrate tolerance in coronary arteries. (5) The results demonstrate that melatonin, acting via specific melatonin receptors, inhibits nitrate tolerance in coronary arteries and that this effect is dependent on the presence of the vascular endothelium.
authors.affiliation: Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND 58105, USA. Stephen.ORourke@NDSU.nodak.edu
authors.forename: Stephen T
authors.initials: ST
authors.lastname: O'Rourke
authors.forename: Hana
authors.initials: H
authors.lastname: Hammad
authors.forename: Philippe
authors.initials: P
authors.lastname: Delagrange
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Scalbert
authors.forename: Paul M
authors.initials: PM
authors.lastname: Vanhoutte
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D001158:Arteries; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D019806:Cromakalim / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000601:surgery; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology; D008550:Melatonin / Q000494:pharmacology* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009281:Naphthalenes / Q000494:pharmacology; D009566:Nitrates / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D005996:Nitroglycerin / Q000009:adverse effects* / Q000494:pharmacology*; D044094:Receptors, Melatonin / Q000037:antagonists & inhibitors / Q000187:drug effects; D013552:Swine; D013618:Tachyphylaxis / Q000502:physiology*; D013997:Time Factors; D014363:Tryptamines / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: C413586:5-methoxycarbonylamino-N-acetyltryptamine; D009281:Naphthalenes; D009566:Nitrates; D044094:Receptors, Melatonin; D014363:Tryptamines; D014665:Vasodilator Agents; D019806:Cromakalim; C106874:N-(2-(1-naphthalenyl)ethyl)cyclobutanecarboxamide; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D005996:Nitroglycerin; D008550:Melatonin; D007545:Isoproterenol