• Biomedical Science Letters
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• v.5 no.1
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• pp.59-66
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• 1999

To evaluate the effect of repeated treatment of xylene on its metabolism, m-xylene (0.25 ml of 50% in olive oi1/100 g body weight) has been intraperitoneally given to the rats 1, 4, 8, 12 and 16 times every other day. m-Xylene was once more administered to the animals after 24 hrs since last injection of it. And then the animals were sacrificed after 24 hrs. Four times xylene treated rats showed the significantly elevated urinary m-methylhippuric acid, compared to those treated with the single dose of m-xylene with the continued similiar high levels of urinary m-methylhippuric acid up to the animals pretreated 12 times and then those treated 16 times defined the significantly decreased urinary m-methylhippuric acid compared to those treated 12 times. On the other hand, hepatic aniline hydroxylase and alcohol dehydrogenase activities demonstrated a gradual increase from the first group to the 12 times xylene-treated animals, but those treated 16 times showed the significantly decreased value compared with the 12 times treated-group. And aldehyde dehydrogenase activities in rats treated with m-xylene 8, 12 or 16 times were significantly decreased compared to those pretreated one or four times. In the early stage of xylene administration, proliferation of SERs were seen whereas SERs were decreased and RERs were clearly increased in xylene-treated rats 16 times. These results indicate that the frequency of xylene injection may influence upon the changes in xylene metabolite, m-methylhippuric acid and it may be due to induction of xylene metabolizing enzymes.