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Mechanism of vasorelaxation induced by Tridax procumbens extract in rat thoracic aorta.

Salahdeen HM, Idowu GO, Salami SA, Murtala BA, Alada AA - J Intercult Ethnopharmacol (2016)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Medicine, Lagos State University, Ikeja, Lagos, Nigeria.

ABSTRACT

Background/aim: 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).

Materials and 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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus

Line graph showing the effects of KT-5720 (50 μM) on cumulative concentration response of Tridax procumbens extract (0.3-1.8 mg/ml) in (a) endothelium-intact (b) endothelium-denuded mesenteric artery pre-contracted with phenylephrine (10–7 M). Data were analyzed using one-way ANOVA followed by Dunnett’s multiple comparison test. (n = 6) (*P < 0.05; **P < 0.01; ***P < 0.001)
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Figure 4: Line graph showing the effects of KT-5720 (50 μM) on cumulative concentration response of Tridax procumbens extract (0.3-1.8 mg/ml) in (a) endothelium-intact (b) endothelium-denuded mesenteric artery pre-contracted with phenylephrine (10–7 M). Data were analyzed using one-way ANOVA followed by Dunnett’s multiple comparison test. (n = 6) (*P < 0.05; **P < 0.01; ***P < 0.001)

Mentions: To assess the role of cGMP and cAMP in the relaxation produced by TPE in aortic rings pre-contracted by PE, we used aortic rings pre-incubated with Rp-8-Br-PET-cGMPS (30 μM) or a selective PKG inhibitor KT-5720 (50 μM) the selective PKA inhibitor in both endothelium-intact and endothelium-denuded rings as pharmacological tools. Under these conditions, the maximum relaxation produced by TPE in endothelium-intact rings was 46.2 ± 4.5%. Pre-incubation for 30 min with the PKG inhibitor Rp-8-Br-PET-cGMPS produced a significant decrease (P < 0.01) from the maximal relaxation elicited by TPE to 12.8 ± 2.7 and 16.7 ± 4.8 % in endothelium-intact and endothelium-denuded, respectively [Figure 3a and b]. Furthermore, pre-incubation with the PKG inhibitor KT-5720 significantly (P < 0.01) inhibited the relaxation induced by TPE in both endothelium-intact and -denuded [Figure 4a and b].


Mechanism of vasorelaxation induced by Tridax procumbens extract in rat thoracic aorta.

Salahdeen HM, Idowu GO, Salami SA, Murtala BA, Alada AA - J Intercult Ethnopharmacol (2016)

Line graph showing the effects of KT-5720 (50 μM) on cumulative concentration response of Tridax procumbens extract (0.3-1.8 mg/ml) in (a) endothelium-intact (b) endothelium-denuded mesenteric artery pre-contracted with phenylephrine (10–7 M). Data were analyzed using one-way ANOVA followed by Dunnett’s multiple comparison test. (n = 6) (*P < 0.05; **P < 0.01; ***P < 0.001)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835993&req=5

Figure 4: Line graph showing the effects of KT-5720 (50 μM) on cumulative concentration response of Tridax procumbens extract (0.3-1.8 mg/ml) in (a) endothelium-intact (b) endothelium-denuded mesenteric artery pre-contracted with phenylephrine (10–7 M). Data were analyzed using one-way ANOVA followed by Dunnett’s multiple comparison test. (n = 6) (*P < 0.05; **P < 0.01; ***P < 0.001)
Mentions: To assess the role of cGMP and cAMP in the relaxation produced by TPE in aortic rings pre-contracted by PE, we used aortic rings pre-incubated with Rp-8-Br-PET-cGMPS (30 μM) or a selective PKG inhibitor KT-5720 (50 μM) the selective PKA inhibitor in both endothelium-intact and endothelium-denuded rings as pharmacological tools. Under these conditions, the maximum relaxation produced by TPE in endothelium-intact rings was 46.2 ± 4.5%. Pre-incubation for 30 min with the PKG inhibitor Rp-8-Br-PET-cGMPS produced a significant decrease (P < 0.01) from the maximal relaxation elicited by TPE to 12.8 ± 2.7 and 16.7 ± 4.8 % in endothelium-intact and endothelium-denuded, respectively [Figure 3a and b]. Furthermore, pre-incubation with the PKG inhibitor KT-5720 significantly (P < 0.01) inhibited the relaxation induced by TPE in both endothelium-intact and -denuded [Figure 4a and b].

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Medicine, Lagos State University, Ikeja, Lagos, Nigeria.

ABSTRACT

Background/aim: 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).

Materials and 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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus