Dose-dependent neurochemical changes during short-term inhalation exposure to m-xylene

Male Wistar were exposed to m-xylene vapor at concentrations of 2.0, 16.1, and 30.3 mumol/1 for 2 weeks (5 days a week, 6 h daily). Xylene concentrations in brain and perirenal fat increased between weeks 1 and 2 of exposure, in proportion to the exposure concentrations. Increase in brain NADPH-diaphorase and azoreductase activities was seen after week 2 at the two higher exposure levels, while superoxide dismutase activity decreased in a dose-related manner at the same time. Biochemical analyses on rats withdrawn from exposure for 2 weeks indicated that the biochemical effects were largely abolished within that time, although cerebral RNA was above the control value at the two higher exposure levels.