Dose dependent effects of chronic exposure to toluene on neuronal and glial cell marker proteins in the central nervous system of rats.

The dose dependent effects of chronic exposure to toluene on the neuronal marker proteins (gamma-enolase, calbindin-D28k) and glial cell marker proteins (alpha-enolase, creatine kinase-B, and beta-S100 protein) were investigated in the central nervous system (CNS) of rats. Three groups of animals were exposed to 100 ppm, 300 ppm, or 1000 ppm toluene vapour eight hours a day, six days a week for 16 weeks. The contents of the marker substances were determined with enzyme immunoassays. A significant increase in the three glial cell marker proteins was noted in the cerebellum after exposure to 100 ppm toluene; a more pronounced increase occurred at the higher toluene concentrations. beta-S100 protein also exhibited a dose dependent increase in the brainstem and spinal cord. On the other hand, the two neuronal cell markers did not show a quantitative decrease in the CNS. This means that the development of gliosis, rather than neurone death, is induced by chronic exposure to toluene. The significant biochemical changes induced around the threshold limit value and the concentration dependent alterations suggest that these nerve specific marker proteins may be used to evaluate solvent related damage to the CNS.