title: [Amiodarone causes endothelium-dependent vasodilation in canine coronary arteries].
abstract: OBJECTIVE
  To assess the vasodilating effects of amiodarone on canine coronary arteries by using solutions of amiodarone dissolved in polysorbate 80 or water.
  
  
  METHODS
  Rings of coronary arteries, with or without intact endothelium, were immersed in Krebs solution and connected to a transducer for measuring the isometric force promoted by a vascular contraction. The arteries were exposed to increasing concentrations of polysorbate 80, amiodarone dissolved in water, amiodarone dissolved in polysorbate 80, and a commercial presentation of amiodarone (Cordarone). The experiments were conducted in the presence of the following enzymatic blockers: only indomethacin, Nomega-nitro-L-arginine associated with indomethacin, and only Nomega-nitro-L-arginine.
  
  
  RESULTS
  Polysorbate 80 caused a small degree of nonendothelium-dependent relaxation. Cordarone, amiodarone dissolved in water, and amiodarone dissolved in polysorbate 80 caused endothelium-dependent relaxation, which was greater for amiodarone dissolved in polysorbate and for Cordarone. Only the association of indomethacin and Nomega-nitro-L-arginine could eliminate the endothelium-dependent relaxation caused by amiodarone dissolved in polysorbate 80.
  
  
  CONCLUSIONS
  The results obtained indicate that vasodilation promoted by amiodarone in canine coronary arteries is mainly caused by stimulation of the release of nitric oxide and cyclooxygenase-dependent relaxing endothelial factors.
authors.affiliation: Faculdade de Medicina de Ribeirão Preto, USP, Ribeirão Preto, SP. alfredo@smnp.usp.br
authors.forename: Alfredo José
authors.initials: AJ
authors.lastname: Rodrigues
authors.forename: Paulo Roberto Barbosa
authors.initials: PR
authors.lastname: Evora
authors.forename: Ayako
authors.initials: A
authors.lastname: Maruo
authors.forename: Hartzell V
authors.initials: HV
authors.lastname: Schaff
mesh_terms: D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D045462:Endothelium-Dependent Relaxing Factors / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005079:Excipients / Q000494:pharmacology; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D019335:Nitroarginine / Q000494:pharmacology; D011136:Polysorbates / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D016861:Cyclooxygenase Inhibitors; D045462:Endothelium-Dependent Relaxing Factors; D004791:Enzyme Inhibitors; D005079:Excipients; D011136:Polysorbates; D019335:Nitroarginine; D000638:Amiodarone; D007213:Indomethacin