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.

Effects of chronic administration of ethanolic extract of kolanut (Cola nitida) and caffeine on vascular function.

BACKGROUND: Kolanut (Cola nitida) is consumed in virtually every part of the world. The caffeine content of kolanut is scarce and the number of investigations studying the health benefits of kolanut is negligible compared to coffee. OBJECTIVE: The present study was designed to identify the caffeine content of kolanut and evaluate the effect of its chronic consumption on cardiovascular functions in rats. METHODS: The caffeine content of kolanut was determined by Gas chromatography-mass spectrometry (GC-MS). Wistar albino rats were divided into four groups (10 Rats/group). Kolanut extract (11.9 mg/kg), caffeine extracted from kolanut (7.5 mg/kg), decaffeinated of kolanut extract (6 mg/kg) and distilled water (control) was administered orally to each group for six-weeks. Effect of treatment on body weight, blood pressure and relaxation response to acetylcholine (ACh) and sodium nitroprusside (SNP) of the aortic rings was assessed. RESULTS: The total caffeine content of kolanut extract was found to be 51% and it was 96% pure from GC-MS analysis. Chronic consumption of kolanut and caffeine significantly (p < 0.05) decreased body weight. Similarly, kolanut extract decaffeinated kolanut and caffeine significantly (p < 0.05) reduced the contractile response to noradrenaline and higher potassium solution. Kolanut extract and caffeine also significantly (p < 0.05) increased the mean arterial blood pressure. Caffeine and kolanut consumption reduced the relaxation response to both acetylcholine and sodium nitroprusside. Atropine and L-NAME considerably inhibit the ACh-induced relaxation of the rat aortic ring suggesting the involvement of cholinergic mechanism. However, indomethacin (10(-4)M) also attenuated the ACh response indicating involvement of protanoids. CONCLUSION: The results suggest that treatment with both kolanut extract and caffeine had similar characteristics between the two groups with no significant differences in the ACh-induced relaxation of thering suggesting that the action of kolanut extract is due to its caffeine content.