title: Toxicokinetics of 14C-atrazine and its metabolites in stage-66 Xenopus laevis.
abstract: Several recent studies have focused on the toxicodynamic implications of amphibian exposure to the commonly used herbicide atrazine (2-chloro-4-ethylamine-6-isopropylamino-s-triazine). These studies are an important part of the risk assessment process; however, the underlying mechanisms of atrazine toxicodynamics are lacking. In an attempt to more fully describe atrazine exposure, the toxicokinetics of atrazine were studied in stage-66 Xenopus laevis larvae. The absorption, distribution, and excretion capacity of these larvae were found to be comparable to those observed in fish. The calculated bioconcentration factor (BCF) was 1.5-1.6 mLwater/glarvae, and by use of whole-body autoradiography, the radiolabel was found to be concentrated in the gall bladder and gastrointestinal tract. Elimination of atrazine was rapid with a half-life of 48 min. The high metabolic capacity of stage-66 X. laevis larvae was demonstrated where, following 8 h of exposure to 14C-atrazine, the percentages of atrazine and its metabolites deethyldeisopropylatrazine (DACT), deisopropylatrazine (DIA), and deethylatrazine (DEA) in larvae, determined by thin-layer chromatography, were 49.8% +/- 3.3%, 9.8% +/- 2.1%, 16.1% +/- 2.5%, and 15.6% +/- 2.0%, respectively. An unknown metabolite(s) was also produced and accounted for the remaining proportion of the total body radioactive residues. This metabolite(s) is hypothesized to be a conjugate of either atrazine or one of its metabolites. These metabolites, namely, DIA, were responsible for the long elimination half-life (72 h) of the total body radioactive residues. These toxicokinetics data would provide better insights in the interpretation of toxicodynamic data.
authors.affiliation: Department of Environmental Biology, University of Guelph, Guelph, Ontario NIG 2W1, Canada. aedginto@uoguelph.ca
authors.forename: Andrea N
authors.initials: AN
authors.lastname: Edginton
authors.forename: Claude
authors.initials: C
authors.lastname: Rouleau
mesh_terms: D000818:Animals; D001280:Atrazine / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity*; D001345:Autoradiography; D002250:Carbon Radioisotopes / Q000378:metabolism; D002855:Chromatography, Thin Layer; D041981:Gastrointestinal Tract / Q000378:metabolism; D006207:Half-Life; D006540:Herbicides / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity*; D007700:Kinetics; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D006540:Herbicides; D001280:Atrazine