Mechanisms Mediating the Vasorelaxing Action of Eugenol, a Pungent Oil, on Rabbit Arterial Tissue

Abstract

The inhibitory actions of eugenol on intracellular Ca2+ concentration ([Ca2+]i) and the contractions induced by excess extracellular K+ concentration ([K+]o) in rabbit thoracic aorta were investigated. Application of excess [K+]o solution (30-90 mM) produced contraction and increased the intensity of the Ca2+ fluorescence signal. Pretreatment with eugenol (> or =0.1 mM) reduced both the amplitude of contraction and the intensity of the Ca2+ fluorescence signal, but the contraction was more strongly affected than the [Ca2+]i. Application of eugenol (0.3 mM) to tissue precontracted by 90 mM [K+]o solution (immediately after the removal of the 90 mM [K+]o solution) slowed the decay of the [Ca2+]i signal, but it did not change the rate of relaxation. Carbonyl cyanide m-chlorophenylhydrozone (10 microM), a mitochondrial metabolic inhibitor, produced a reduction in tension despite a slight increase in [Ca2+]i when applied to muscle precontracted by 90 mM [K+]o solution. These results indicate that eugenol relaxes the rabbit thoracic aorta while suppressing the Ca2+-sensitivity and both the uptake and extrusion mechanisms for Ca2+. To judge from the similarities between its actions and those of metabolic inhibitors, eugenol may produce its actions at least partly through metabolic inhibition.

Vasorelaxant effects of eugenol on rat thoracic aorta

“…These observations are consistent with reports suggesting that eugenol and other phenolic compounds may act as a calcium antagonist (Nishijima et al, 1998(Nishijima et al, , 1999.…”

“…These observations suggested that eugenol might interfere with both voltage-and receptor-operated Ca 2+ channels reducing the Ca 2+ influx, and consequently, contraction. These results are in accordance to those found by Nishijima et al (1998Nishijima et al ( , 1999 using eugenol concentration higher than 0.1 mM, in rabbit aortic rings precontracted by high K + solution, and with those found by Lin et al (1999) using isoeugenolol (a eugenol isomer), in rat thoracic aorta precontracted by PHE and high K + solution.…”

“…The concentrations which produce effects against PHE-and Ca 2+ -induced contractions are in the mM range, a concentration similar to the ones used by other authors (Nishijima et al, 1999). Even though, until now eugenol or related compounds are not considered as a vasodilator that could be used as a pharmacological agent.…”

Eucalyptol, an essential oil, reduces contractile activity in rat cardiac muscle

“…However, direct actions of eucalyptol on the cardiac muscle or contractile proteins were not described yet. Moreover, other compounds of essential oils, such as eugenol and isoeugenol, produce vasodilatation (27,28) and depress cardiac contractions acting via calcium channels (29). Our results show that eucalyptol reduced the isometric force developed by papillary muscles in a dose-dependent manner.…”

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.…”