Mechanism of vasorelaxation induced by Tridax procumbens extract in rat thoracic aorta.
OBJECTIVE
Tridax procumbens (Linn) (Asteraceae) is one of the herbs widely distributed in many parts of the world. Its leaves have long been used for the treatment of hypertension in Nigeria. Previous studies have shown that aqueous leaves of T. procumbens extract (TPE) lowers blood pressure through endothelium-dependent and -independent mechanism in the aortic rings isolated from normotensive rats. The aim of the present study was to further investigate mechanisms of TPE-induced relaxation in the aortic artery by assessing its mechanistic interactions with nitric oxide (NO) synthase, cyclic guanosine monophosphate (cGMP), and cyclic adenosine monophosphate (cAMP).


METHODS
The aortic artery isolated from healthy, young adult normotensive Wistar albino rats (250-300 g) were pre-contracted with phenylephrine (PE) (10-7 M) and KCl (60 mM) and were treated with various concentrations of aqueous extract of TPE (0.5-9.0 mg/ml). The changes in arterial tension were recorded using Ugo Basile model 7004 coupled to data capsule acquisition system model 17400. The interaction between TPE with cAMP and cGMP inhibitors was also evaluated.


RESULTS
The results showed that the TPE (0.5-9.0 mg/ml) significantly (P < 0.05) reduced the contraction induced by PE in a concentration-dependent manner. The vasorelaxant effect caused by the TPE was significantly (P < 0.05) attenuated with pre-incubation of cGMP (Rp-8Br PET cGMPS) and cAMP (Rp-AMP) inhibitor, respectively.


CONCLUSIONS
These results suggest that TPE causes vasodilatory effects in a concentration-dependent manner in the isolated rat aortic artery. The mechanism of action of TPE is complex. A part of its relaxing effect is mediated directly by blocking or modulating cGMP and cAMP.
Department of Physiology, College of Medicine, Lagos State University, Ikeja, Lagos, Nigeria.
Hussein Mofomosara
HM
Salahdeen
Department of Physiology, Olabisi Onabanjo University, Ogun State, Nigeria.
Gbolahan O
GO
Idowu
Department of Physiology, College of Medicine, Lagos State University, Ikeja, Lagos, Nigeria.
Shakiru A
SA
Salami
Department of Physiology, College of Medicine, Lagos State University, Ikeja, Lagos, Nigeria.
Babatunde A
BA
Murtala
Department of Physiology, University of Ibadan, Ibadan, Nigeria.
AbdulRasak A
AA
Alada
Cyclic adenosine monophosphate inhibitor; Rp-8Br PET cyclic guanosine monophosphate; Tridax procumbens; cyclic guanosine monophosphate inhibitor; vasorelaxant effect