EFFECT OF INTRA-TRACHEAL INSTILLATION AND INHALATION OF SILICON DIOXIDE ON SOME BIOCHEMICAL VARIABLES IN BRONCHO-ALVEOLAR LAVAGE FLUID AND LUNG HISTOPATHOLOGY IN RATS

Abstract

In the present study, the bronchial alveolar lavage fluid (BALF) bio chemical and lung histopathological changes occurring in response to single large intra-tracheal exposure to silica have been compared to the changes seen after continued chronic exposure via inhalation. Male albino rats (200-250gms) were exposed to silicon dioxide via intra-tracheal instillation (8mg/0.05ml saline) and whole body inhalation (200mg/m3, 6 hours/day for 2 and 4 weeks) in separate groups. The respective control animals were instilled with normal saline (0.05 ml) or exposed to fresh air in simulation chamber for the same duration. BALF was analyzed for total protein, elastase, malondialdehyde (MDA) levels and catalase activity and histopathology of right lung was carried out after 4 weeks post-exposure in intra-tracheal model and after 2 and 4 weeks of exposure in the inhalation model. The levels of total protein, elastase and malondialdehyde (MDA) were significantly elevated, while catalase activity was significantly decreased in the BALF of exposed animals as compared to controls. The histopathological studies of lungs, showed exudates of inflammatory cells, chiefly of macrophages in the alveolar spaces and interstitial septa with multifocal nodular granu-lomatous lesions. The biochemical findings in BALF of both the models indicate inflammatory changes, lipid peroxidation and fibrosis. However, comparatively lower catalase activity and higher elastase levels in the 4 week inhalationally exposed group than the 4 week post intra-tracheally exposed group, suggests that these parameters may be affected by acute and chronic exposure and require further confirmation.