＜正＞ AIM: The present study was aimed to examine the role of endothelial nitric oxide in the relaxant response to green tea （-）epicatechin and its modulation of endothelium-mediated relaxation in the isolated rat mesenteric artery rings. METHODS: Changes in the isometric tension were measured with Grass force-displacement transducers. RESULTS: The （-）epicatechin-induced relaxation was largely dependent on the presence of intact endothelium and was re-versed by NG-nitro-L-arginine methyl ester 10 μmol/L or methylene blue 10 μmol/L, the inhibitors of nitric oxide-mediated relaxation. L-Arginine at 1 mmol/L antagonized the effect of L-NAME or methylene blue. Pretreatment of endothelium-intact rings with （-）epicatechin 10 μmol/L enhanced the relaxation induced by endothelium-dependent vasodilator, acetylcholine, while this concentration did not influence the endothelium-independent relaxation in-duced by sodium nitroprusside in the endothelium-denuded artery rings. CONCLUSION: The results indicate that the en
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