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KMID : 0382420010270020010
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Korean Journal of Environmental Health Society
2001 Volume.27 No. 2 p.10 ~ p.16
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Effect of Circadian Rhythms on the Xylene Metabolizing Enzyme Activities in Rats
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Lee Hye-Ja
Yoon Chong-Guk
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Abstract
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To evaluate an effect of circadian variation on the xylene metabolizing enzyme activities, 50% m-xylene in olive oil(0.25 ㎖/100 g body weight) was intraperitoneally administered to the rats every other day for 6 days both in the night; 24:00 and the day; 12:00. Then animals were sacrificed at 8 hr after last injection of m-xylene. Hepatic microsomal cytochrome P450 contents were more increased both in control and xylene treated rats of night phase than those of day phase. But the activity of hepatic alcohol dehydrogenase(ADH) in control of night phase showed the similar value with that in those of day phase and xylene treated rats of day phase showed an increasing tendency of hepatic ADH activity as those of night phase showing similar activity. Furthermore, hepatic aldehyde dehydrogenase(ALDH) activity compared with control was found to be higher tendency in control rats of night phase than those of day phase. And by xylene treatment, enzyme activities of rats of day phase were higher tendency in rats of control but those of night phase were somewhat inhibited. Besides, xylenetreated animals of night phase showed increasing tendency of urinary methylhippuric acid concentration compared with those of day phase. On the other hand, liver weight per body weight(%), hepatic lipid peroxide content and serum xanthine oxidase activity were higher in night phase than day phase. And the activities of hepatic oxygen free radical metabolizing enzymes such as xanthine oxidase, gluthathione S-transferase, glutathione peroxidase and superoxide dismutase and glutathione content were generally higher both in control and xylene-treated rats of night phase than those of day phase.
In conclusion, it can be hypothesized on the basis of the results. that the accumulation rate of m-xylene intermediate metabolite, i.e. m-methylbenzaldehyde in liver tissus may be higher in night phase than in day phase and it may be responsibie for higher liver toxicity in night phase than in day phase
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