Potassium channels and prostacyclin contribute to vasorelaxant activities of Tridax procumbens crude aqueous leaf extract in rat superior mesenteric arteries.

BACKGROUND: Previous studies have shown that aqueous extract of the leaf of Tridax procuinbens 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 procuinbens 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 (250-300 g) were precontracted with phenylephrine (PE) (10(-7) M) and potassium chloride (KCl) (60 mM) and were treated with Various concentrations of aqueous extract ofT procumbens (0.9.0 mg/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 GG-MS revealed the presence of linoleic acid. The T. procumbens extract (TPE) ranging from 0.5-9.0 mg/mI 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 (1(-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 synthaseinhibitor (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 Ga2+ activated potassium channels. The observed effect of this extract may be probably due to the presence of linoleic acid in this extract.