| Research Abstract |
The workers handling organic solvents are often exposed to mixture of them. Neurotoxicity of n-hexane is well known to be enhanced by co-exposure of MEK. We made clear that neurotoxicity of n-hexane was decreased be co- exposure of toluene. The modification and mechanism of neurotoxicity of n-hexane by co-exposure of other solvents were studied and the results are as follows;
1) Urinary 2,5-hexanedione, one of n-hexane metabolites, was decreased by co-exposure of MEK in proportion to the concentration of MEK, 2,5-hexanedione in blood was remarkably decreased by co-exposure of MEK, too. The hypothesis that co-exposure of MEK facilitates metabolism of n- hexane and increase, of production of 2,5-hexanedione resulting in enhancement of neurotoxicity of n-hexane seems doubtful from our results.
2) In order to evaluate the long-term effects of co-exposure of solvents, an automated solvent exposure system for small laboratory animals was devised. Single and mixed exposure of n-hexane and tolue
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ne were successfully conducted for one day exposure and for long-term exposure. But the exposure system was found not to work well in the long-term exposure of MEK. Therefore, the experiment of the long-term co-exposure of n-hexane and MEK was interrupted and the system was improved.
The long-term co-exposure started again and continues now. 3) As indices for neurotoxicity of organic solvents, nervous system specific proteins, analysis and S-100 proteins were determined in the peripheral nerves, cerebrum, cerebellum and brain stem. The results showed that these nervous system specific proteins were useful indices of the effects on the nervous system. 4) The method to determine urinary 2,5-hexanedione was established by us in order to determine it more exactly and specifically. It was revealed that pH of sample urine should be decreased to less than 1 at the pretreatment in order to obtain a stable 2,5-hexanedione, and 2,5- hexanedione was hardly detected in the urine of the person unexposed to n- hexane and the good co-relation between n-hexane exposure and urinary 2,5- hexanedione was obtained using the appropriate column. Less
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