Inhibition of Nitric-Oxide Synthase Enhances Antigen-Induced Contractions and Increases Release of Cysteinyl-Leukotrienes in Guinea Pig Lung Parenchyma: Nitric Oxide as a Protective Factor

Nitric oxide (NO) in exhaled air is a biomarker of airway inflam-mation. However, the role of NO in the peripheral lung is not known. The aim of this study was to determine the role of endogenous NO in antigen-induced contractions of ovalbumin (OVA)-sensitized guinea pig lung parenchyma (GPLP). The con-traction in this in vitro model of the peripheral lung closely resembles the corresponding response in human airways. Cu-mulatively increasing concentrations (10–10,000 g/l) of OVA induced concentration-dependent contractions of the GPLP that were enhanced by the NO synthase (NOS) inhibitors N-nitro-L-arginine (L-NOARG; 100 ), N-monomethyl-L-argi-nine (100 M), N-nitro-L-arginine methyl ester (100 ), and N-(3-(aminomethyl)benzyl)acetamidine (1400W; 1 ). The en-hancement induced by L-NOARG was reversed by coadminis