The exact mechanism of rapid loss of RRF on HD is not fully understood. Several experimental and clinical studies showed that variety of vascular events and increased oxidative stress in dialysis patients may be due to inhibition of nitric oxide (NO) synthesis by ADMA (Asymmetric Dimethylarginine ), known to be endogenous inhibitor of NO synthetase [4]. ADMA may be significantly reduced by dialysis [5]. Metabolism of ADMA is primarily by the enzyme DDAH , which activity is decreased by inflammation, oxidative stress, diabetes mellitus and hypercholesterolemia [6].