Plasma concentrations of asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, are elevated in sickle cell patients but do not increase further during painful crisis.

Plasma concentrations of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are elevated in the clinically asymptomatic state of sickle cell disease (SCD). However, the role of ADMA during vaso-occlusive complications has not been defined. ADMA concentrations were determined in HbSS (n = 43) and HbSC (n = 25) patients with healthy blood donors (HbAA) as controls. In the clinically asymptomatic state ADMA concentrations were elevated in sickle cell patients as compared to healthy controls (HbSS 0.70 micromol/L, HbSC 0.54 micromol/L, HbAA 0.39 micromol/L) (P < 0.001). Yet plasma ADMA concentrations did not increase further at presentation with a painful crisis implicating no role of primary importance during vaso-occlusive crises.