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Inhaled silica dust increases nitric oxide and cytokine production associated with collagen synthesis and fibrosis in rats.
Dey-RD; Stanley-C; Blackford-JA Jr.; Harness-J; Durham-J; Castranova-V; Hubbs-A
Appl Occup Environ Hyg 1996 Jul; 11(7):914-918
Pulmonary responses in the rat to the inhalation of occupationally applicable levels of silica (14808607) were studied. Specific pathogen free male Fischer-rats were exposed to 2.0mg/m3 silica for 8 hours/day, 5 days per week, for periods of 2 weeks, 2 months, or 6 months. Bronchoalveolar lavage cells were extracted and analyzed for cellular differentials, chemiluminescence, platelet derived growth factor (PDGF), transforming growth factor beta (TGFbeta), and messenger RNA (mRNA) levels of inducible nitric-oxide (NO) synthase (iNOS). Northern analysis revealed mRNA levels for iNOS to be increased after 2 months, but returned to normal at 6 months. An increase in red blood cells and leukocytes revealed pulmonary damage and inflammation after 2 and 6 months of exposure. An increase in total and NO dependent chemiluminescence revealed that oxygen radicals and NO were produced by bronchoalveolar lavage cells after 2 and 6 months. Multiple granulomatous lesions and an increase in collagen synthesis were observed after 6 months, and TGFbeta mRNA levels were also elevated after 6 months; however, PDGF mRNA remained comparable to controls. The authors conclude that the inhalation of silica at concentrations that could occur in the mining and sandblasting industry may present a health concern due to this study's findings that significant pulmonary inflammation and fibrosis occur in rats exposed to occupationally relevant levels of silica.
NIOSH-Author; Silica-dusts; Lung-fibrosis; Laboratory-animals; Dust-inhalation; Occupational-exposure; Alveolar-cells; Lung-function; Pulmonary-function; Histopathology; Inhalation-studies; Immune-reaction
Issue of Publication
Applied Occupational and Environmental Hygiene
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division