Анотація
Background: Previous studies have shown that aqueous extract of the leaf of Tridax procumbens is capable of lowering blood pressure through its vasodilatory effects. In the present study attempt was made to examine the biological active components of T. procumbens leaf using GC-MS methods. We further investigated the role of K+ channels in the vasorelaxation effects of Tridax procumbens using rat isolated mesenteric artery.
Methods: The superior mesenteric artery isolated from healthy, young adult Wistar rats (250-300g) were precontracted with phenylephrine (PE) (10-7M) and potassium chloride (KCl) (60mM) and were treated with various concentrations of aqueous extract of T. procumbens (0.5- 9.0mg/ml). The changes in arterial tension were recorded using a force – displacement transducer (Model 7004; Ugo Basil Varese, Italy) coupled to data capsule acquisition system.
Results: The results of GC-MS revealed the presence of linoleic acid. The T. procumbens extract (TPE) ranging from 0.5- 9.0mg/ml significantly (p<0.05) reduced the contraction induced by (PE) and (KCl) in a concentration-dependent manner. The extract also antagonised the calcium-induced vasoconstriction (10-9-10- 5) in calcium-free with high concentration of potassium as well as in calcium- and potassium free physiological solutions. The vasorelaxing effect caused by TPE was significantly (p<0.05) attenuated with preincubation of potassium channels blockers (Barium chloride and apamin), NO synthase inhibitor (L-NAME), prostacyclin inhibitor (indomethacin), atropine, propranolol, and methylene blue while it was not affected by preincubation with glibenclamide and tetra ethyl ammonium, 4-aminopyridine (4-AP) and oxadiazolo quinoxalin (ODQ).
Conclusion: The results of this study demonstrate that T. procumbens extract causes vasodilatory effects by blocking calcium channels and the vasodilatory effect of the extract may also be due to stimulation of prostacyclin production and opening of small- conductance Ca2+ activated potassium channels. The observed effect of this extract may be probably due to the presence of linoleic acid in this extract.
Keyword: Tridax procumbens, potassium channels blockers, prostacyclin,
Résumé
Contexte: Des études antérieures ont montré que l’extrait aqueux de la feuille de Tridax procumbens est capable de diminuer la pression sanguine à travers ses effets vasodilatateurs. Dans la présente étude, tentative a été faite pour examiner les composants actifs biologiques de feuille T. procumbens en utilisant des méthodes GC-MS. Nous avons également étudié le rôle des canaux K + dans les effets vasorelaxation de Tridax procumbens en utilisant l’artère mésentérique de rat isolé.
Méthodes: L’artère mésentérique supérieure isolé de sain, jeune adulte rats Wistar (250-300g) ont été prétraitées avec phényléphrine (PE) (10-7 M) et chlorure de potassium (KCl) (60mM) et ont été traités avec diverses concentrations aqueuse d’extrait de T. procumbens (0,5 - 9.0mg / ml). Les variations dans la tension artérielle ont été enregistrés en utilisant une force - déplacement transducteur (modèle 7004; Ugo Basile Varese, Italie) couplé au système d’acquisition de la capsule des données.
Résultats: Les résultats de GC-MS ont révélé la présence d’acide linoléique. L’extrait de T. procumbens (TPE) allant de 0,5 à 9.0mg / ml a de façon significative (p <0,05) réduit la contraction induite par (PE) et (KCl) d’une manière dépendante à la concentration. L’extrait a également été un antagoniste à la vasoconstriction induite par le calcium (10-9-10-5) en calcium libre avec forte concentration de potassium, ainsi que dans des solutions physiologiques de calcium- et potassium libre. L’effet vasorelaxant causée par TPE a été significativement (p <0,05) atténuée avec la pré incubation des canaux de blocage potassiques (chlorure de baryum et apamine), inhibiteur synthéase NO (L-NAME), inhibiteur prostacycline (indométacine), l’atropine, le propranolol, et méthylène bleu tandis qu’il n’a pas été affectée par une pré incubation avec glibenclamide et tetrathlammnium, 4- aminopyridine (4-AP) et oxadiazolo quinoxalin (ODQ).
Conclusion: Les résultats de cette étude démontrent que l’extrait de T. procumbens provoque des effets vasodilatateurs en bloquant les canaux calciques et l’effet vasodilatateur de l’extrait peut aussi être due à la stimulation de la production de prostacycline et ouverture petites conductance de canaux potassiques Ca2+ activés. L’effet observé de cet extrait peut être probablement due à la présence d’acide linoléique dans cet extrait.
Mot-clés: Tridax procumbens, canaux potassiques bloquants, la prostacycline
Correspondence: Dr. H.M. Salahdeen, Department of Physiology, (Smooth Muscles Research Group) Lagos State University College of Medicine, Ikeja, Lagos, Nigeria. E-mail: hmsalahdeen@gmail.com; hussein.salahdeen@lasycom.edu.ng
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