NOS2 and chronic kidney disease: Asymmetrical dimethylarginine (ADMA), a competitive NOS inhibitor that causes reduced NO production, and its enantiomer symmetric dimethylarginine (SDMA) have been observed to accumulate in the early stages of CKD and kidney failure (Zoccali et al., 2001; Kielstein et al., 2002; Fleck et al., 2003; Busch et al., 2006; Brooks et al., 2008; El-Sadek et al., 2016).