Several of the luminal endothelial glycocalyx functions are exerted via interactions with glycosidic components and sugar binding proteins with lectinic activity. One important example is the mannose receptor (MR). The MR has been detected in cell types that mediate the phagocytosis and pinocytosis of particles and solutes containing mannose. Using isolated constant pressurized rat mesenteric arteries (RMA), we evaluated the effects of a mannose polymer in the vascular tone. RMA were pre-contracted with 10 micromol/L phenylephrine and carbohydrates were perfused at 20 microliters/min. Perfusion of free D-mannose (1 nmol/L to 100 micromol/L) induced a concentration-dependent vasodilation of pre-contracted RMA. Perfusion of mannose polymer (1 nmol/L to 100 micromol/L) induced a larger effect in a concentration-dependent vasodilation. Mannose polymer's maximum effect reached a 96 percent of basal diameter; this significant vasodilation was not nitric oxide (NO) or cyclooxygenase (COX) dependent effect. We corroborated the binding of the mannose polymer to the endothelial lumen, by perfusion of a fluorescently labeled mannose polymer; and also, we detected a significant level of MR mRNA in whole mesenteric arteries. With all these, we proposed a novel effect of a MR in the regulation of vascular tone.