Preliminary kinetics and metabolism of 2,4,6-trinitrotoluene and its reduced metabolites in an aquatic oligochaete
| Autor: | Thomas W. La Point, Alethea T. Bowen, Jason M. Conder |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Analysis of Variance
biology Chemistry Health Toxicology and Mutagenesis Metabolite Fresh Water Bioconcentration Aquatic Science biology.organism_classification Tubifex Dinitrobenzenes chemistry.chemical_compound Biotransformation Environmental chemistry Tubifex tubifex Animals Trinitrotoluene Toxicokinetics Carbon Radioisotopes Steady state (chemistry) Oligochaeta Chromatography High Pressure Liquid |
| Zdroj: | Aquatic Toxicology. 69:199-213 |
| ISSN: | 0166-445X |
| Popis: | 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 ( 14 C ) TNT revealed that only 15–47% of 14 C -TNT equivalents were identified as TNT, 2ADNT, or 4ADNT, indicating significant metabolism and/or binding to biomolecules. Of unidentified 14 C -TNT equivalents, 28–38% remained unextractable. Both unextractable and extractable unidentified substances increased throughout the 54 h 14 C -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. |
| Databáze: | OpenAIRE |
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