Tridax procumbens leaf extract elicits relaxation of rat mesenteric artery by activation of Na+ -K+ ATPase / Na+ - Ca2+ exchangerShakiru Ademola Salami, Hussein Mofomosara Salahdeen, Gbolahan Olabisi Idowu, Babatunde Adekunle Murtala, Abdul Rasak Akinola Alada3.
Background: Tridax procumbens leaf extract has been reported to show antihypertensive actions through its vasodilatory effects. Although several mechanisms of action have been reported, the sub-cellular mechanism of action of the extract is yet to be fully elucidated.
Aim and Objectives: In this study, we investigate the involvement of Na+ - K+ -pump and Na+- Ca2+ exchanger in the vasorelaxant activities of T. procumbens extract (TPE) in isolated rat superior mesenteric arteries.
Materials and Methods: Superior mesenteric artery isolated from healthy, young adult Wistar rats (250300 g) and pre-contracted with phenylephrine (PE) (10-7M) were treated with various concentrations of aqueous extract of TPE (0.59 mg/mL). The changes in arterial tension were recorded and interaction between TPE with the selective blocker of Na+ - K+ ATPase (ouabain) and putative Na+-Ca2+ exchanger inhibitor (NiCl2) was evaluated.
Results: The result indicated that TPE significantly inhibit the cumulative concentration response curves to PE (10-9 - 10-5 M) in a concentration-dependent manner. Pre-treatment with both ouabain and nickel chloride (NiCl2), abolished the vasorelaxant responses of TPE. Furthermore, TPE reduced the relaxant effect with decreased extracellular Na+ concentration. TPE-induced vasorelaxation was completely abolished in a Na+ -free solution, a condition that eliminates the influence of the forward mode of the exchanger.
Conclusion: The results provide direct hypothetical evidence that the activation of Na+ - K+ ATPase and stimulation of the forward mode of the Na+-Ca2+ exchanger contribute to the vasorelaxation induced by TPE in mesenteric artery.
Key words: Mesenteric Artery; Na+- K+- ATPase; Na+ - Ca2+ exchanger; Tridax procumbens