title: Epoxybutene-hemoglobin adducts in rats and mice: dose response for formation and persistence during and following long-term low-level exposure to butadiene.
abstract: Measurement of specific adducts to hemoglobin can be used to establish the dosimetry of electrophilic compounds and metabolites in experimental animals and in humans. The purpose of this study was to investigate the dose response for adduct formation and persistence in rats and mice during long-term low-level exposure to butadiene by inhalation. Adducts of 3,4-epoxy-1-butene, the primary metabolite of butadiene, with N-terminal valine in hemoglobin were determined in male B6C3F1 mice and male Sprague-Dawley rats following exposure to 0, 2, 10, or 100 ppm of 1,3-butadiene, 6 h/day, 5 days/week for 1, 2, 3, or 4 weeks. Blood samples were collected from groups of five mice and three rats at the end of each week during the 4 weeks of exposure and weekly for 3 weeks following the end of the 4-week exposure period. The increase and decrease, respectively, of the adduct levels during and following the end of the 4-week exposure followed closely the theoretical curve for adduct accumulation and removal for rats and mice, thereby demonstrating that the adducts are chemically stable in vivo and that the elimination follows the turnover of the red blood cells. The adduct level increased linearly with butadiene exposure concentration in the mice, whereas a deviation from linearity was observed in the rats. For example, after exposure to 100 ppm butadiene, the epoxybutene-hemoglobin adduct levels were about four times higher in mice than in rats; at lower concentrations of butadiene, the species difference was less pronounced. Blood concentrations of epoxybutene, estimated from hemoglobin adduct levels, were in general agreement with reported concentrations in mice and rats exposed by inhalation to 62.5 ppm. These studies show that adducts of epoxybutene with N-terminal valine in hemoglobin can be used to predict blood concentration of epoxybutene in experimental animals.
authors.affiliation: Chemical Industry Institute of Toxicology (CIIT), Research Triangle Park, North Carolina 27709, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Osterman-Golkar
authors.forename: O
authors.initials: O
authors.lastname: Moss
authors.forename: A
authors.initials: A
authors.lastname: James
authors.forename: M S
authors.initials: MS
authors.lastname: Bryant
authors.forename: M
authors.initials: M
authors.lastname: Turner
authors.forename: J A
authors.initials: JA
authors.lastname: Bond
mesh_terms: D000465:Algorithms; D000818:Animals; D019540:Area Under Curve; D015415:Biomarkers; D001711:Biotransformation; D002070:Butadienes / Q000737:chemistry / Q000493:pharmacokinetics*; D002138:Calibration; D004305:Dose-Response Relationship, Drug; D004852:Epoxy Compounds / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D015415:Biomarkers; D002070:Butadienes; D004852:Epoxy Compounds; D006454:Hemoglobins; C024370:3,4-epoxy-1-butene