Luteolin is a flavonoid with antioxidant properties already demonstrated in 
studies related to inflammation, tumor, and cardiovascular processes; however, 
there are no available information regarding its antioxidant effects at the 
venous endothelial site. We investigated the effects of luteolin (10, 20, and 
50 μmol/L) in cultures of rat venous endothelial cells. Nitric oxide (NO) and 
reactive oxygen species (ROS) were analyzed by fluorimetry; 3-nitrotyrosine 
(3-NT) residues were evaluated by immunofluorescence, and prostacyclin (PGI2) 
release was investigated by colorimetry. Intracellular NO levels were 
significantly enhanced after 10 min of luteolin incubation, with a parallel 
decrease in ROS generation. These results were accompanied by a significant 
reduction in the expression of 3-NT residues and enhanced PGI2 rates. Therefore, 
luteolin is effective in reducing ROS thereby improving NO availability in 
venous endothelial cells. Besides, luteolin-induced decrease in 3-NT residues 
may correlate with the enhancement in endothelial PGI2 bioavailability. These 
findings suggest the future application of this flavonoid as a protective agent 
by improving endothelial function in several circulatory disorders related to 
venous insufficiency.