NOS3 and endothelial dysfunction: Because decreased NOS3 expression is related to endothelial dysfunction (Napoli and Ignarro, 2001; Napoli et al., 2006), we investigated the possible association between the rs2070744, rs 1799983, and rs79467411 single nucleotide polymorphisms (SNPs) in the NOS3 gene and the risk for RLS in Caucasian Spanish people.