Metabolism of 1,3-butadiene: species differences.

Species differences in the metabolism of 1,3-butadiene (BD) have been studied in an effort to explain the major differences observed in the responses of mice, the sensitive species, and rats, the resistant species, to the toxicity of inhaled BD. BD is metabolized by the same metabolic pathways in all species studied, but there are major species differences in the quantitative aspects of those pathways. Of the species studied, mice are the most efficient at metabolizing BD to the initial metabolite, the monoepoxide (BDO). Mice either convert most of the BDO to the diepoxide (BDO2), the most mutagenic of the BD metabolites, or form conjugates of the BDO with glutathione (GSH). Rats, on the other hand, are less active at forming BDO, oxidize very little of the BDO to BDO2, and form GSH conjugates with either the BDO or its hydrolysis product, butenediol. Primates convert even less of inhaled BD to BDO and hydrolyze most of the BDO to the butenediol. The extent to which primates form BDO2 is unknown. Because of the association of high levels of the highly mutagenic BDO2 with the sensitive rodent strain, it is important to determine the production of this metabolite in primates, particularly humans.