EPO and endothelial dysfunction: EPO increases oxidative stress in the arterial wall.31 In human coronary artery endothelial cells, EPO at 5 and 20 IU/mL decreased NO production in response to acetylcholine stimulation, with a parallel reduction in endothelial NO synthase protein abundance.6 In agreement, we found that tempol, a superoxide dismutase mimetic, partially prevented endothelial dysfunction induced by EPO.