Recent studies have shown that the involvement of NOS and ARG in ADPKD progression is linked with: renal production of L-Arg, L-Arg metabolization by different pathways, renal alteration of protein activity/stability/expression, DDHA inactivation and increase in ADMA levels, reduction in renal NO production, and biphasic regulation of NO. The gene discussed is NOS2; the disease is autosomal dominant polycystic kidney disease.