Species and tissue differences in the microsomal oxidation of 1,3-butadiene and the glutathione conjugation of butadiene monoxide in mice and rats. Possible role in 1,3-butadiene-induced toxicity.

Rat and mouse liver, lung, and kidney microsomes metabolized 1,3-butadiene to butadiene monoxide (BM), whereas microsomes from testis, one of the target organs of 1,3-butadiene toxicity in both species, were ineffective. 1,3-Butadiene metabolism was NADPH-dependent and inhibited by 1-benzylimidazole. With mouse microsomes, a 4-fold higher rate was measured with kidney compared with liver or lung, which exhibited similar rates. With rat microsomes, the rate obtained with liver was 2- and 6-fold higher than those of lung and kidney, respectively. Overall, oxidation rates by mouse tissues were higher than those of rat tissues. These results, along with the finding that BM was stable in the presence of rat plasma, provide evidence for the role of circulating metabolites in 1,3-butadiene-induced toxicity. Furthermore, crotonaldehyde, a known carcinogen, was detected with mouse tissues only. Thus, in addition to the greater ability of mouse tissues to produce BM, formation of crotonaldehye may contribute to the greater susceptibility of mice to 1,3-butadiene toxicity compared with rats. Nearly all rat liver glutathione S-transferase activity was localized to the cytosol (greater than 96%). BM glutathione conjugation rates with liver cytosol of both species were similar, whereas conjugation rates with mouse lung and kidney cytosol were 4- and 2-fold higher than those of rat lung and kidney, respectively. Thus, species differences in BM glutathione conjugation do not correlate with species susceptibility.(ABSTRACT TRUNCATED AT 250 WORDS)