Nitric oxide is not a mediator of inflammation-induced resistance to atracurium

Resistance to atracurium as a result of increased drug binding to alpha(1)-acid glycoprotein is associated with increased inducible nitric oxide synthase activity and increased nitric oxide levels in plasma. We investigated if the inhibition of inducible nitric oxide synthase and suppression of nitric oxide can reverse the resistance to atracurium. As a model of alpha(1)-acid glycoprotein and nitric oxide increase, 84 male Sprague-Dawley rats received an IV injection of either 60 mg/kg Corynebacterium parvum (CP) or saline (control). The 2 groups (CP/Control) were further divided into subgroups, receiving the selective inducible nitric oxide synthase inhibitor, N-Iminolysine, via drinking water at different concentrations. On day 4 post-CP injection, the pharmacodynamics of atracurium were determined. Plasma concentrations of nitric oxide, atracurium, and alpha(1)-acid glycoprotein were measured and acetylcholine receptor numbers were quantified. In the CP groups, N-Iminolysine suppressed nitric oxide levels in a dose-dependent manner. Resistance to atracurium persisted. alpha(1)-acid glycoprotein serum levels remained increased in all CP groups with no differences in acetylcholine receptor expression. Our results suggest that the mechanism leading to increased expression of alpha(1)-acid glycoprotein and consecutive increased protein binding of atracurium is not mediated by inducible nitric oxide synthase induction and nitric oxide expression.