Lysosomal enzyme activity and fibroblast stimulation of lavage from guinea pigs exposed to silica dust.

Guinea pigs were exposed to silica dust for 3 weeks and examined up to 1 year thereafter. The activity of several lysosomal enzymes in lung lavage fluid (LLF) increased from 8 weeks after cessation of exposure whereas the level in aveolar macrophages decreased. Collagen synthesis in fibroblast cultures exposed to LLF was also increased except at 24 weeks after exposure. The results indicate that 8 weeks and later after cessation of exposure to silica dust there are cellular changes in the lung which can be related to the exposure, although typical silicotic lesions were not observed till 1 year after the exposure.