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Lung inflammation and damage after silica inhalation in rats: is there recovery?
Porter-DW; Robinson-VA; Ramsey-D; Khan-A; McLaurin-JL; Teass-A; Mercer-RR; Castranova-V
Toxicologist 2000 Mar; 54(1):318
Crystalline silica (quartz) is a well established lung inflammatory and fibrogenic occupational dust. Although the pulmonary effects of silica exposure in animal models has been well studied, the relationships between silica exposure and clearance (recovery) on lung inflammation and damage has not been investigated. To investigate these relationships, rats were exposed to filtered air (control) or 15 mg/m3 silica aerosol (6 hours/day, 5 days/week). Rats were exposed for 20, 40, or 60 days and each exposure group had a corresponding exposure plus 36 day recovery group. Rat lungs were lavaged to isolate bronchoalveolar lavage (BAL) cells and acellular BAL fluid, while samples of whole blood were collected to monitor peripheral leukocytes. Pulmonary inflammation was monitored by measuring BAL polymorphonuclear leukocytes (PMN). BAL PMN cell counts were elevated in silica-exposed versus control rats, and PMN counts increased further during recovery. Blood leukocyte counts displayed a pattern similar to the BAL PMN counts. Silica cytotoxicity was measured by analyses of BAL fluid lactate dehydrogenase (LDH) activity and albumin (ALB) concentration. BAL fluid LDH activities and ALB concentrations were higher in silica-exposed versus control rats, and these parameters continued to increase during recovery. These data indicate that progressively severe silica-induced lung inflammation and damage occurs in response to the duration of silica inhalation and these processes continue after silica exposure has ended.
Lung-disorders; Silica-dusts; Silicates; Inhalation-studies; Laboratory-animals; Animals; Animal-studies; Quartz-dust; Dusts; Dust-inhalation; Occupational-exposure; Aerosols; Pulmonary-system-disorders; Respiratory-system-disorders; Fibrous-dusts; Fibrogenesis; Fibrogenicity; Fibrosis
Issue of Publication
The Toxicologist. Society of Toxicology 39th Annual Meeting, March 19-23, 2000, Philadelphia, Pennsylvania