Visual toxicity of toluene--an experimental study
Ikeda, K.
Nippon Ganka Gakkai Zasshi 91(10): 903-910
1987
ISSN/ISBN: 0029-0203 PMID: 3442276 Document Number: 292841
It has been suggested that inhalation of toluene in humans might produce ocular toxicity, therefore, in the present study, the biochemical and electrophysiological effects of toluene were studied in male Wistar rats. Each rat inhaled 90ppm of toluene for 12 hours per day for a duration of one to two weeks. Quantitative determination of toluene within rat tissues was measured by means of gas chromatography. The concentration, i.e., residue of toluene was extremely high in the optic nerve both at one or two weeks after the inhalation of toluene. The residue of toluene was still remarkably higher in the optic nerve, even at two weeks after the withdrawal of toluene. Electroretinogram (ERG) showed the initial depression of the amplitudes of both a- and b- waves at one week after the start. These findings were more remarkable in rats with two weeks of inhalation. These were observed till three weeks after the discontinuation of toluene inhalation. Four weeks after withdrawal, recovery and improvement were seen in the amplitudes of the a-wave and the b-wave. Six weeks after withdrawal, the ERG was completely normalized. The results of visual evoked potential (VEP) due to flash stimulation showed that prolongation of the latency time of the N2 component was observed at two weeks after the inhalation. The prolongation was not improved even at four weeks afterwards. The above results suggested that the involvement of visual pathway was located mainly at the optic nerve, since dissociated change was observed in the ERG and in the flash VEP. In order to find out the possible toxic effects of metabolites, benzyl alcohol and benzaldehyde onto the VEP were examined. The rats were subcutaneously given 2 mg per day of benzyl alcohol or 4 mg per day of benzaldehyde for two weeks. No prolongation of the latency time of the N2 component could be noted. The metabolites of toluene had no effect on the visual pathway. In conclusion, toluene manifested direct toxicity on the optic nerve.