[Effect of bronchoalveolar lavage fluid on silica-induced alveolitis in rats]

An experimental silicosis model was produced in rats by intratracheal instillation of 25 mg silica dioxide normal saline. Animals were killed at 1, 3, 7, 14, 45 days after treatment, for cytological, enzyme cytochemical and biochemical analyses of the bronchoalveolar lavage fluid. The results showed that the number of polymorphonuclear cells and alveolar macrophages (AMs) increased continuously. The total amount of protein and activities of LDH and AcP in the lavage fluid were elevated, while the activities of LDH, SDH and AcP demonstrated by enzyme cytochemical staining in AMs were lowered. The survival rate of AMs decreased and foamy AMs appeared, these changes reflected the main characteristics of silica-induced alveolitis. We conclude that silica-induced alveolitis is not only the essential pathological characteristics of early pulmonary reaction to silica, but also plays a crucial role in the pathogenesis of silicotic fibrosis.