title: The role of endothelium in the calcium-induced reduction of the contractile response of the rabbit aorta.
abstract: 1. Increase of Ca2+ concentration in the bath solution diminishes the contractile response of isolated rabbit aorta rings to alpha 1-adrenoceptor agonists and KCl. 2. In intact preparations the contractions of methoxamine and phenylephrine were maximal when a 0.3- to 0.6-mM Ca2+ bath solution was used, and those of KCl were maximal with a 2.5-mM Ca2+ concentration. 3. The contractions of methoxamine and phenylephrine also were decreased by increasing the Ca2+ concentration above 1.25 mM in disrupted endothelium preparations and in those incubated in indomethacin (10(-5) M), N omega-nitro-L-arginine methyl ester (10(-4) M), or methylene blue (10(-6) M). 4. High organ bath Ca2+ concentrations also caused a decrease in KCl contractions using endothelium-denuded and the treated preparations, the responses being similar with 1.25 mM and 2.5-mM Ca2+ in the methylene blue-treated preparations, whereas they were greater with 1.25 mM Ca2+ in the others.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Complutense University Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ortega
authors.forename: M
authors.initials: M
authors.lastname: Puerro
authors.forename: V
authors.initials: V
authors.lastname: Lopez-Miranda
authors.forename: A
authors.initials: A
authors.lastname: Aleixandre
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008729:Methoxamine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D004791:Enzyme Inhibitors; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D011189:Potassium Chloride; D019001:Nitric Oxide Synthase; D008729:Methoxamine; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester