Vasorelaxant effects of eugenol on rat thoracic aorta

Abstract

Eugenol is a natural pungent substance and the main component of clove oil, with vasorelaxant action. To elucidate some of the possible mechanisms involved in this action isometric tension was measured in aortic rings from male Wistar rats precontracted with phenylephrine (PHE, 10 À7 M) or KCl (75 mM). Responses to increasing concentrations of eugenol (10 À6 -10 À2 M) were obtained in the presence and absence of endothelium. In the presence of eugenol, dose -response curves to PHE (10 À9 to 10 À4 M) and KCl (5 -125 mM) were displaced downwards. Concentration-dependent relaxation was observed in rings precontracted with PHE (10 À7 M) and KCl (75 mM). The tension increment produced by increasing external calcium concentration (0.25 -3 mM) was also reduced by eugenol (300 mM) treatment. The inhibitory effects of eugenol (300 mM) were compared to those induced by nifedipine (0.01 mM), a selective Ca 2+ channel blocker, producing similar relaxant effects. Two other protocols were performed. After precontraction with PHE (10 À7 M), increasing concentrations of eugenol (10 À6 -10 À2 M) were used before and after N w -nitro-L-arginine (L-NAME, 10 À4 M) and methylene blue (10 À5 M) treatment. Eugenolinduced relaxation was reduced by endothelial damage (rubbing), L-NAME and methylene blue treatments. Results suggested that eugenol produces smooth muscle relaxation resulting from the blockade of both voltage-sensitive and receptor-operated channels that are modulated by endothelial-generated nitric oxide. D

Vanillin and Vanillin Analogs Relax Porcine Coronary and Basilar Arteries by Inhibiting L-Type Ca2+Channels

“…Like other natural compounds (e.g., carvacrol, eugenol, and thymol), natural or synthetic VA or EtVA can activate TRPV3 channels (Xu et al, 2006;Vriens et al, 2008Vriens et al, , 2009. Vascular effects of TRPV3 agonists other than VA and its analogs have been reported (Nishijima et al, 1999;Damiani et al, 2003;Earley et al, 2010;Peixoto-Neves et al, 2010. For example, both carvacrol and eugenol reduce the myogenic tone of cerebral arteries coexpressing endothelial TRPV3 and TRP channel receptor ankyrin 1 (TRPA1) (Earley et al, 2010) and relax rat thoracic aortae contracted with phenylephrine or KCl (Damiani et al, 2003), respectively.…”

“…Vascular effects of TRPV3 agonists other than VA and its analogs have been reported (Nishijima et al, 1999;Damiani et al, 2003;Earley et al, 2010;Peixoto-Neves et al, 2010. For example, both carvacrol and eugenol reduce the myogenic tone of cerebral arteries coexpressing endothelial TRPV3 and TRP channel receptor ankyrin 1 (TRPA1) (Earley et al, 2010) and relax rat thoracic aortae contracted with phenylephrine or KCl (Damiani et al, 2003), respectively. The relaxation to carvacrol is endothelium-dependent and inhibited by the nonspecific TRP channel blocker ruthenium red but not by the specific TRPA1 inhibitor HC-030031 [theophylline-7-(N-4-isopropylphenyl) acetamide]; it is accompanied by hyperpolarization of and reduction of the intracellular calcium concentration in the vascular smooth muscle cells (Earley et al, 2010).…”

“…The relaxation to carvacrol is endothelium-dependent and inhibited by the nonspecific TRP channel blocker ruthenium red but not by the specific TRPA1 inhibitor HC-030031 [theophylline-7-(N-4-isopropylphenyl) acetamide]; it is accompanied by hyperpolarization of and reduction of the intracellular calcium concentration in the vascular smooth muscle cells (Earley et al, 2010). Relaxations to eugenol are partially sensitive to endothelium removal, and inhibition of either NOS or sGC (Damiani et al, 2003). By contrast, in our study, relaxations to VA and its analogs in porcine arteries were independent of the presence of the endothelium, resistant to inhibitors of NOS, sGC, or hyperpolarizing potassium channels (discussed earlier), and were not prevented by ruthenium red, which inhibits all TRPVs and other types of TRPs (Nilius et al, 2007;Vriens et al, 2009) including TRPV3 channels (Earley et al, 2010).…”

Correlation of antioxidative properties and vaso-relaxation effects of major active constituents of traditional Chinese medicines

“…After equilibration, the aortic rings were challenged with phenylephrine (1 M). After the establishment of a sustained contraction caused by phenylephrine, individual compounds (3 M-3 mM) were added cumulatively to the organ baths and the concentration-response curves to each compound were constructed (Cao et al, 2006;Damiani et al, 2003). A 100% relaxation was considered when the active tension returned to the basal level.…”

Vasodilating Effect of Di-Peptides in Thoracic Aortas from Spontaneously Hypertensive Rats

“…They were then progressively stretched to a preloaded tension of 2 g followed by equilibration for another 45 min until stabilized. 6) In all experiments, after 45 min equilibration, aorta rings were challenged with 30 mM KCl to ensure viability the of the preparation. To prepare rings without an endothelium layer, the layer was removed mechanically by gentle scraping with a stainless-steel wire.…”