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Nitric oxide production by rat bronchoalveolar macrophages or polymorphonuclear leukocytes following intratracheal instillation of lipopolysaccharide or silica.

Huffman-LJ; Prugh-DJ; Millecchia-L; Schuller-KC; Cantrell-S; Porter-DW
J Biosci 2003 Feb; 28(1):29-37
Exposure of the lung to lipopolysaccharide (LPS) or silica results in an activation of alveolar macrophages (AMs), recruitment of polymorphonuclear leukocytes (PMNs) into bronchoalveolar spaces, and the production of free radicals. Nitric oxide (NO) is one of the free radicals generated by bronchoalveolar lavage (BAL) cell populations following either LPS or silica exposure. The purpose of the present study was to assess the relative contributions of AMs and PMNs to the amounts of NO produced by BAL cells following intratracheal (IT) instillation of either LPS or silica. Male Sprague Dawley rats (265-340 g body wt.) were given LPS (10 mg/100 g body wt.) or silica (5 mg/100 g body wt.). BAL cells were harvested 18-24 h post-IT and enriched for AMs or PMNs using density gradient centrifugation. Media levels of nitrate and nitrite (NOx; the stable decomposition products of NO) were then measured 18 h after ex vivo culture of these cells. Following IT exposure to either LPS or silica, BAL cell populations were ~ 20% AMs and ~ 80% PMNs. After density gradient centrifugation of BAL cells from LPS- or silica-treated rats, cell fractions were obtained which were relatively enriched for AMs (~ 60%) or PMNs (~ 90%). The amounts of NOx produced by the AM-enriched fractions from LPS- or silica-treated rats were ~ 2-4-fold greater than that produced by the PMN-enriched fractions. Estimations of the relative contribution of AMs or PMNs to the NOx produced indicated that: (i) following LPS treatment, 75%-89% of the NOx was derived from AMs and 11%-25% from PMNs; and (ii) following silica treatment, 76%-100% of the NOx was derived from AMs and 0-24% from PMNs. Immunohistochemistry for inducible NO synthase on lung tissue sections supported these findings. We conclude that AMs are the major source of the NO produced by BAL cells during acute pulmonary inflammatory responses to LPS or silica.
Pulmonary-disorders; Pulmonary-function-tests; Lung-irritants; Lung-disorders; In-vivo-studies; Nitrates; Animal-studies; Respiratory-system-disorders; Pulmonary-system-disorders; Laboratory-animals
Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia 26505
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Journal Article
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Disease and Injury: Fertility and Pregnancy Abnormalities
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Journal of Biosciences