The toxic effects of combined exposure to toluene and m-xylene in animals. IV. Liver ultrastructure after subchronic inhalatory exposure.

Abstract

The effects of combined inhalatory exposure to m-xylene and toluene on the rat hepatocytes were investigated. Limited proliferation of smooth endoplasmic reticulum and increase of the number of lysosomes were observed in hepatocytes after 3-months of single exposure to 1000 ppm of m-xylene and toluene. Moreover, mitochondria increased in most of hepatocytes. After combined exposure to mixture of m-xylene and toluene at concentrations of 500 + 500 ppm, respectively, the types of ultrastructural changes in hepatocytes followed the pattern observed after exposure of each of the single organic solvent. However, proliferation of the smooth endoplasmic reticulum was more eminent. The hepatocytes ultrastructure of rats exposed to 100 ppm of m-xylene and toluene for 6 months were similar to that observed in rats exposed to 1000 ppm of m-xylene for 3 months. In rats exposed to a mixture of m-xylene and toluene for 6 months, the ultrastructural changes in hepatocytes were a combination of those observed after a single exposure to each of the organic solvent. It may be concluded that changes in the hepatocytes ultrastructure were an adaptive rather than a toxic effect. Because in the case of combined exposures the doses were half of those used in single exposures, the additive effect on the proliferation of smooth endoplasmic reticulum was observed in the rat liver after combined exposure to toluene and m-xylene using electron microscopy.