Bovine bronchial epithelial cells metabolize L-arginine to L-citrulline: Possible role of nitric oxide synthase

The conversion of L-arginine to L-citrulline is catalyzed by nitric oxide synthase (NOS), and results in the release of nitric oxide (NO). We hypothesized that bronchial epithelial cells metabolize L-arginine to L-citrulline. We found that cell lysates obtained from unstimulated, cultured bovine bronchial epithelial cells (BBECs) converted L-[³H]arginine to L-[³H]citrulline. This conversion was attenuated by three competitive NOS inhibitors and modulated by lipopolysaccharide and cigarette smoke extract (p<0.01, all comparisons). These data demonstrate that BBECs metabolize L-arginine to L-citrulline and implicate a role for the L-arginine:NOS biosynthetic pathway in modulating airway responses.