J Bone Metab.  2015 May;22(2):57-69. 10.11005/jbm.2015.22.2.57.

The Effect of Eqoul, a Metabolite of Isoflavone, on Endothelial Cell-independent Vasodilatation of Human Uterine Artery In Vitro

• Kim JY
• Lee MY
• Park HM

• KMID: 2170089
• DOI: http://doi.org/10.11005/jbm.2015.22.2.57

Abstract

BACKGROUND
The purpose of this study is to investigate 1) whether equol has the direct modulation on vascular tone of endothelium-denuded human uterine artery, and 2) if present, whether this equol-induced modulation of vascular tone is mediated by intracellular calcium modulation through Ca2+ & K+ channels on vascular smooth muscle cell membrane.
METHODS
The uterine arteries were obtained at the time of hysterectomy from 15 women. The uterine smooth muscles were pretreated with phenylephrine, 10(-5) M & high KCl solution 70 mM. The equol at 6 different concentrations from 10(-11) to 10(-6) M were used for the evaluation of modulatory action of equol on precontracted vascular smooth. The cumulative concentration-response for equol were determined on phenylephrine-induced contractions and compared with the results without pretreatment.
RESULTS
Equol 10(-11) to 10(-6) M in concentration showed relaxation effect on vascular smooth muscle contraction which was induced by phenylephrine 10(-5) M. This relaxation effect of equol was dose-dependent. Equol in same concentrations showed no significant effects on vascular smooth muscle contraction induced by high KCI solution. Phenylephrine-induced contraction was markedly reduced from 10(-7) to 10(-4) M in concentration by pretreatment of equol, but high KCI-induced contraction was not affected by pretreatment of equol.
CONCLUSIONS
This vasodilatation effect of equol may be induced by calcium antagonistic action, which was mediated through antagonistic action for receptor-dependent Ca2+ channel, but not for voltage-dependent Ca2+ channel. As far as we know, this is the first report of phytoestrogen equol on vascular reactivity of human vessels.

Keyword

Equol; Vasodilation; Mucsle smooth

MeSH Terms

Calcium
Cell Membrane
Equol
Female
Humans
Hysterectomy
Muscle, Smooth
Muscle, Smooth, Vascular
Phenylephrine
Phytoestrogens
Relaxation
Uterine Artery*
Vasodilation*
Calcium
Equol
Phenylephrine
Phytoestrogens

Figure

• 

  Fig. 1 Typical representation of equol-induced response of human uterine arterial strip on precontracted status by phenylephrine (10-5 M). Cumulative application of equol evoked dose-dependent relaxation. PE, phenylephrine.

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  Fig. 2 Typical representation of equol-induced response of human uterine arterial strip on precontracted status by high concentration of KCl (70 mM). Cumulative application of equol evoked no remarkable change.

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  Fig. 3 Effects of 10-8 M equol-pretreatment on the phenylephrine-induced contractures. The responses were decreased and the effects were statistically significant (n=8, *means P<0.05).

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  Fig. 4 Effects of 10-8 M equol-pretreatment on the high KCl-induced contractures. The tensions of contracture above than 35 mM were rarely affected by the pretreatments (n=8).

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  Fig. 5 Effects of 10 mM tetraethyl ammonium-pretreatment on the equol-induced relaxations. TEA rarely affected the relaxations (n=12).

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  Fig. 6 Effects of 10-5 M 4-AP-pretreatment on the equol-induced relaxations. 4-AP rarely affected the relaxations (n=8).

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