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01.02.2013 | Original Contribution | Ausgabe 1/2013

European Journal of Nutrition 1/2013

Endothelium/nitric oxide mechanism mediates vasorelaxation and counteracts vasoconstriction induced by low concentration of flavanols

European Journal of Nutrition > Ausgabe 1/2013
Annalisa Aggio, Davide Grassi, Eugenia Onori, Antonio D’Alessandro, Francesco Masedu, Marco Valenti, Claudio Ferri



At relatively low concentrations, flavanols induce inconsistent effects on isolated arterial tone, sometimes explained as being due to a structure–activity relationship. The aim of our study was to investigate the effects of two flavanols at different doses on arterial functional state.


The effects of two catechins, (−)-epigallocatechin-3-gallate (EGCG) and (−)-epicatechin (EP), on rat-isolated aorta tone were investigated on resting tension and on precontracted preparations, both in the presence and in the absence of endothelium.


At resting tension, endothelium-intact preparations, EGCG and EP (0.01–10 μM), induced a slight concentration-dependent, non-significant contraction. On endothelium-denuded preparations, both EGCG and EP induced a concentration-dependent contraction (significance at 0.1 and 1 μM concentrations of the two compounds, respectively). In phenylephrine (PE) (1 μM) precontracted, endothelium-intact preparations, EGCG and EP (0.01–10 μM), induced a concentration-dependent vasorelaxation, reaching significance at 1 μM concentration of both agonists. On endothelium-denuded preparations, EGCG and EP did not significantly affect PE (0.3 μM)-induced tone. In endothelium-intact precontracted preparations, Nω nitro-l-arginine (L-NNA), a nitric oxide synthase (NOS) activity inhibitor, abolished the vasorelaxant effect of EGCG and EP (0.01–10 μM). At high concentrations, EGCG and EP (100 μM) elicited a marked relaxation. This was significantly larger in the presence than in the absence of endothelium or in the presence of L-NNA.


Our findings highlight the important role played by an endothelium/NO-mechanism in the regulation of basal tone and in both mediating vasorelaxation and counteracting vasoconstriction induced by low concentrations of flavanols in rat thoracic aorta.

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