Irreversible effects of xylene on the brain after long term exposure: a quantitative study of DNA and the glial cell marker proteins S-100 and GFA.

Mongolian gerbils (Meriones ungiculatus) were exposed by continuous inhalation to xylene at 160 or 320 ppm for three months, followed by a four month post-exposure solvent-free period. Concentrations of the two astroglial proteins, S-100 and GFA, as well as DNA, were then determined in different regions of the gerbil central nervous system. After exposure at 320 ppm, both concentrations of GFA and S-100 were found increased in the frontal cerebral cortex, whereas in the cerebellar vermis, only the GFA concentrations were significantly increased. In the posterior cerebellar vermis increased DNA concentrations were found after exposure at both 160 and 320 ppm, indicating an increased cell density, probably due to a proliferation of cells. These results indicate that xylene is a neurotoxin, inducing signs compatible with the presence of astrogliosis in distinct regions of the gerbil brain.