title: Analysis of the role of nitric oxide in the relaxant effect of the crude extract and fractions from Eugenia uniflora in the rat thoracic aorta.
abstract: This study has evaluated the possible role played by the L-arginine-nitric oxide pathway in the vasorelaxant action of the hydroalcoholic extract from Eugenia uniflora, and fractions from the extract, in rings of rat thoracic aorta. The addition of an increasing cumulative concentration of hydroalcoholic extract from E. uniflora (1-300 micrograms mL-1) caused a concentration-dependent relaxation response in intact endothelium-thoracic aorta rings pre-contracted with noradrenaline (30-100 nM). The IC50 value, with its respective confidence limit, and the maximum relaxation (Rmax) were 7.02 (4.77-10.00) micrograms mL-1 and 83.94 +/- 3.04%, respectively. The removal of the endothelium completely abolished these responses. The nitric oxide synthase inhibitors N omega-nitro-L-arginine (L-NOARG, 30 microM) and N omega-nitro-L-arginine methyl ester (L-NAME, 30 microM), inhibited the relaxation (Rmax) to -10.43 +/- 7.81% and -3.69 +/- 2.62%, respectively. In addition, L-arginine (1 mM), but not D-arginine (1 mM), completely reversed inhibition by L-NOARG. Methylene blue (30 microM), a soluble guanylate cyclase inhibitor, reduced the relaxation induced by the extract to 14.60 +/- 7.40%. These data indicate that in the rat thoracic aorta the hydroalcoholic extract, and its fractions, from the leaves of E. uniflora have graded and endothelium-dependent vasorelaxant effects.
authors.affiliation: Department of Pharmacology, Universidade Federal de Santa Catarina Florianópolis, Brazil.
authors.forename: E
authors.initials: E
authors.lastname: Wazlawik
authors.forename: M A
authors.initials: MA
authors.lastname: Da Silva
authors.forename: R R
authors.initials: RR
authors.lastname: Peters
authors.forename: J F
authors.initials: JF
authors.lastname: Correia
authors.forename: M R
authors.initials: MR
authors.lastname: Farias
authors.forename: J B
authors.initials: JB
authors.lastname: Calixto
authors.forename: R M
authors.initials: RM
authors.lastname: Ribeiro-Do-Valle
mesh_terms: D000438:Alcohols / Q000737:chemistry; D000818:Animals; D001013:Aorta, Thoracic; D005591:Chemical Fractionation; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007928:Lethal Dose 50; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000438:Alcohols; D004791:Enzyme Inhibitors; D010936:Plant Extracts; D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester