Visfatin is a novel adipocyte-derived cytokine. We hypothesized that visfatin could directly affect vascular reactivity. To test the hypothesis, effects of visfatin on contraction of isolated blood vessels were examined. In endothelium-intact rat aorta, pretreatment with visfatin (100 ng/ml, 30 min) inhibited noradrenaline (NA; 1 nM-1 mu M)-induced contraction. In NA (100 nM)-pre-contracted aorta, visfatin (1-100 ng/ml) directly induced a relaxation. Although an N-G-Nitro-L-arginine methyl ester (300 mu M, 15 min) inhibited the relaxation, an insulin receptor inhibitor, AGL2263 (10 mu M, 20 min) was ineffective. Visfatin (100 ng/ml, 20 min) induced a phosphorylation of eNOS at serine 1177 and a de-phosphorylation of eNOS at threonine 495. Visfatin also induced a phosphorylation of Akt at serine 473 and a substrate of cGMP-dependent protein kinase, vasodilator stimulated phosphoprotein at serine 239. Present study revealed for the first time that visfatin has a vasodilating effect on isolated blood vessels, which is mediated via endothelium-derived NO. (C) 2009 Elsevier Inc. All rights reserved.