Abstract
1,3-Butadiene is produced commercially for use in the manufacture of elastomers, polymers and other chemicals. Recent inhalation carcinogenicity studies of butadiene indicate that B6C3F1 mice are more sensitive to the tumorigenic effects of inhaled butadiene than are Sprague Dawley rats. The purpose of this investigation was to determine if there were differences in distribution in tissues of inhaled butadiene between rats and mice. Male Sprague Dawley rats and B6C3F1 mice were exposed nose-only for 3.4 hr to (mean±SE) 1220±71 µg 14HC-butadiene/L air and 121±2 µg 14C-butadiene/L air, respectively. Radioactivity was distributed widely in tissues immediately following exposure of both rats and mice to 14C-butadiene. In both species, respiratory tract tissue (lung, trachea, nasal turbinates), gastrointestinal tract (small and large intestine), liver, kidneys, urinary bladder and pancreas contained high concentrations of radioactivity within 1 hr after the end of exposure. In all cases, tissues of mice contained 15 to 100 times the concentration of 14C-butadiene equivalents per µmole of butadiene inhaled than did rats. For both rats and mice, elimination of 14C from tissues and blood was rapid, with 77% to 99% of the initial tissue burden being eliminated with half-times of 2 to 10 hr. Within 1 hr after the end of exposure, all rat tissues retained a substantial amount of 14C that was associated with volatile material (20% to 40% of the total 14C in tissues) that was probably butadiene and/or metabolites. A similar observation was noted in mouse liver, the only tissue of mice examined. The data indicate that there were no apparent differences between rats and mice in tissue depots for 14C derived from butadiene, but that, per µmole of butadiene inhaled, tissues of mice attained significantly greater concentrations of 14C than did rats.