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Effects of acute and chronic nitric oxide inhibition in an experimental model of chronic pulmonary allergic inflammation in guinea pigs.

Prado CM, Leick-Maldonado EA, Kasahara DI, Capelozzi VL, Martins MA, Tibério IF

Department of Medicine, University of São Paulo, Brazil.

Endogenously produced nitric oxide is a recognized regulator of physiological lung events, such as a neurotransmitter and a proinflammatory mediator. We tested the differences between chronic and acute nitric oxide inhibition by N(omega)-nitro-L-arginine methyl ester (L-NAME) treatment in lung mechanics, inflammation, and airway remodeling in an experimental asthma model in guinea pigs. Both acute and chronic L-NAME treatment reduced exhaled nitric oxide in sensitized animals (P < 0.001). Chronic L-NAME treatment increased baseline and maximal responses after antigen challenge of respiratory system resistance and reduced peribronchial edema and mononuclear cells airway infiltration (P < 0.05). Acute administration of L-NAME increased maximal values of respiratory system elastance and reduced mononuclear cells and eosinophils in airway wall (P < 0.05). Chronic ovalbumin exposure resulted in airway wall thickening due to an increase in collagen content (P < 0.005). Chronic nitric oxide inhibition increased collagen deposition in airway wall in sensitized animals (P < 0.05). These data support the hypothesis that in this model nitric oxide acts as a bronchodilator, mainly in proximal airways. Furthermore, chronic nitric oxide inhibition was effective in reducing edema and mononuclear cells in airway wall. However, airway eosinophilic inflammation was unaltered by chronic L-NAME treatment. In addition, nitric oxide inhibition upregulates collagen deposition in airway walls.

Published 8 September 2005 in Am J Physiol Lung Cell Mol Physiol, 289(4): L677-83.
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