title: Xanthorrhizol induces endothelium-independent relaxation of rat thoracic aorta.
abstract: Xanthorrhizol, a bisabolene isolated from the medicinal plant Iostephane heterophylla, was assayed on rat thoracic aorta rings to elucidate its effect and likely mechanism of action, by measuring changes of isometric tension. Xanthorrhizol (1, 3, 10, 30 and 100 microg/mL) significantly inhibited precontractions induced by KCI-; (60mM), noradrenaline (10(-6) M) or CaCl2 (1.0 mM). Increasing concentrations of external calcium antagonized the inhibitory effect on KCl-induced contractions. The vasorelaxing effect of xanthorrhizol was not affected by indomethacin (10 microM) or L-NAME (100 microM) in intact rat thoracic aorta rings precontracted by noradrenaline, which suggested that the effect was not mediated through either endothelium-derived prostacyclin (PGI2) or nitric oxide release from endothelial cells. Endothelium removal did not affect the relaxation induced by xanthorrhizol on rat thoracic aorta rings, discarding the participation of any substance released by the endothelium. Xanthorrhizol inhibitory effect was greater on KCI- and CaCl2-induced contractions than on those induced by noradrenaline. Xanthorrhizol inhibitory effect in rat thoracic aorta is likely explained for interference with calcium availability by inhibiting calcium influx through both voltage- and receptor-operated channels.
authors.affiliation: UIM Farmacologica, Hospital de Especialdades, Centro Medico Nacional Siglo XXI; IMSS, Col. Narvarte, Mexico.
authors.forename: M G
authors.initials: MG
authors.lastname: Campos
authors.forename: M V
authors.initials: MV
authors.lastname: Oropeza
authors.forename: T
authors.initials: T
authors.lastname: Villanueva
authors.forename: M I
authors.initials: MI
authors.lastname: Aguilar
authors.forename: G
authors.initials: G
authors.lastname: Delgado
authors.forename: H A
authors.initials: HA
authors.lastname: Ponce
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010636:Phenols / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology; D018517:Plant Roots / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D010636:Phenols; D010936:Plant Extracts; D014662:Vasoconstrictor Agents; C120248:xanthorrhizol; D011189:Potassium Chloride; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine; D007213:Indomethacin