['The aims of this study were to determine hyperoxia effects on S-nitrosothiol (SNO) accumulation and L-type amino acid transporter 1 (LAT1) expression/function in alveolar epithelium and to determine whether hyperoxia impairs exogenous nitric oxide (NO) treatment effects in alveolar epithelium through effects on LAT1 expression and/or function.', 'SNO accumulation in vitro and in vivo after NO treatment was dependent on the LAT1 system transport. Hyperoxia (60% or 90%) impaired NO effects on SNO accumulation and soluble guanylyl cyclase activation in proportion to the magnitude of hyperoxia and the duration of exposure, up to 12\u2009h, in type I-like (R3/1) and type II-like (L2) rat and human (A549) alveolar epithelial cells. LAT function, determined by sodium-independent (3)H-leucine uptake, was impaired in a parallel manner. Hyperoxia impaired LAT1 expression in alveolar epithelial cells, determined by immunoblots and immunofluorescence, and in newborn rats exposed to 60% O2 for 4 days, determined by immunohistochemistry.', 'Despite significant preclinical evidence, inhaled NO has shown disappointing limitations in clinical applications. Our studies suggest an important explanation: oxidative stress, a common feature of diseases in which therapeutic NO would be considered, impairs LAT1 expression and function, blocking a major route for inhaled NO (iNO) action, that is, the uptake of S-nitrosocysteine via LAT1.'] Does hyperoxia inhibit nitric oxide treatment effects in alveolar epithelial cells via effects on L-type amino acid transporter-1?