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Metabolism of vinyltoluene in the rat: effect of induction and inhibition of the cytochrome P 450

Metabolism of vinyltoluene in the rat: effect of induction and inhibition of the cytochrome P 450. Heinonen, Tuula H. H. (Dep. Ind. Hyg. Toxicol., Inst. Occup. Health, Helsinki SF-00290/29, Finland). Biochem. Pharmacol., 33(10), 1585-93 (English) 1984. CODEN: BCPCA6. ISSN: 0006-2952. DOCUMENT TYPE: Journal CA Section: 4 (Toxicology) Metab. of p-vinyltoluene (I) [622-97-9] was studied in rats after injecting different doses of I. The main metabolites excreted in urine of rats after I treatment were: thioethers, p-methylmandelic acid [18584-20-8], p-methylphenylglyoxylic acid [7163-50-0], p-methylbenzoyl glycine [27115-50-0], p-methylphenylacetyl glycine [91419-97-5], and p-vinylbenzoyl glycine [85434-97-5]. The highest excretion rate was obtained with doses of 50, 250, and 500 mg/kg already within the 1st 6 h. However, the dose of 500 mg/kg did not increase the excretion rates of these metabolites compared to the dose of 250 mg/kg suggesting that the metabolite pathways begin to be satd. with the amt. of 250 mg/kg. At 50 mg/kg, 55% of the dose was detected as urinary metabolites within 23 h, mainly within the 1st 6 h. The amts. of the excreted metabolites expressed as percent of the injected dose (250 or 500 mg/kg) were lower than that caused by 50 mg/kg, and a noticeable amt. 622-97-9 is just another one chemical used in this study. of the total sums were excreted within 11-23 h suggesting that the excretion was still continued with the doses of 250 and 500 mg/kg 23 h after the injection. The excretion of all analyzed metabolites of I was prevented by the pretreatment of the rats with 1-phenylimidazole [7164-98-9], an inhibitor of cytochrome P 450 monooxygenases. This indicates that these metabolites were formed as catalyzed by cytochrome P 450. The structures of the analyzed metabolites suggest that the main reactive intermediate of I is vinyltoluene-7,8-oxide [13107-39-6]. Furthermore, the amts. of the excreted metabolites showed that the main detoxification pathways of vinyltoluene-7,8-oxide were the conjugation with reduced glutathione and hydration to diols. Pretreatment of the rats with PCBs increased the excretion rates of the metabolites. However, the PCB-pretreated rats excreted less thioethers (62%) compared to the rats treated only with the same amt. of I whereas the total sum of the other metabolites was about the same in these groups. Thus, PCBs change the metab. of I to some other pathway which could be glucuronide conjugation because PCBs increased the activity of UDP-glucuronosyltransferase in a dose-dependent manner. .