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Preliminary kinetics and metabolism of 2,4,6-trinitrotoluene and its reduced metabolites in an aquatic oligochaete
Conder, J.M.; La Point, T.W.; Bowen, A.T. (2004). Preliminary kinetics and metabolism of 2,4,6-trinitrotoluene and its reduced metabolites in an aquatic oligochaete. Aquat. Toxicol. 69(3): 199-213. dx.doi.org/10.1016/j.aquatox.2004.04.013
In: Aquatic Toxicology. Elsevier Science: Tokyo; New York; London; Amsterdam. ISSN 0166-445X, more
Peer reviewed article  

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Keywords
    Biotransformation; Elimination; Elimination; Explosives; Tubifex tubifex (Müller, 1774) [WoRMS]; Marine

Authors  Top 
  • Conder, J.M.
  • La Point, T.W.
  • Bowen, A.T.

Abstract
    We examined the toxicokinetics and metabolism of 2,4,6-trinitirotoluene (TNT) and four of its major reduced metabolites (2-amino-4,6-dinitrotoluene (2ADNT), 4-amino-2,6-dinitrotoluene (4ADNT), and 2,4-diamino-6-nitrotoluene (2,4DANT)) in the freshwater, aquatic oligochaete Tubifex tubifex exposed to spiked, reconstituted water. In uptake experiments with each compound, steady state concentrations were reached within 1 h, and all absorbed compounds were completely eliminated in 0-3 h. The appearance of 2ADNT and 4ADNT (from metabolism of absorbed TNT) was five times slower, reaching 95% of steady state in 14.2-16.1 h. Approximately, 82% of absorbed TNT was metabolized to ADNTs; metabolism to 4ADNT was favored over 2ADNT by a factor of 3. No further metabolism of ADNTs to DANTs was detected. After a loss of 29-50% of metabolically-generated ADNTs during the first hour of the TNT depuration experiment, Tubifex ADNT concentrations remained constant throughout the 53 h depuration period. This suggests differences between the toxicokinetics of absorbed ADNTs and the toxicokinetics of metabolically-generated ADNTs. Experiments using radiolabeled (14C) TNT revealed that only 15-47% of 14C-TNT equivalents were identified as TNT, 2ADNT, or 4ADNT, indicating significant metabolism and/or binding to biomolecules. Of unidentified 14C-TNT equivalents, 28-38% remained unextractable. Both unextractable and extractable unidentified substances increased throughout the 54 h 14C-TNT uptake experiment. The unidentified portions of the radiolabel were not eliminated during a 53-h depuration experiment. Bioconcentration factors (BCFs) for HPLC-detectable compounds were found to be linearly related to log KOW (r2 = 0.9963). BCFs for 2ADNT, 4ADNT, and 2,4DANT were 10.22, 12.41, and 2.75, respectively. The BCF for TNT was 12.25, based on a molar sum of total TNT and its metabolites (∑TNT + 2ADNT + 4ADNT), and 2.53 based on TNT only. Compound hydrophobicity predicted the toxicokinetics and bioconcentration of compounds absorbed from water, however, the large discrepancy between the toxicokinetics of absorbed versus metabolically-generated ADNTs and the bioconcentration and toxicokinetics of the unidentified substances warrant further investigation

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