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CHARACTERIZATION OF METABOLITES IN SMALL FISH BIOFLUIDS AND TISSUES BY NMR SPECTROSCOPY
Citation:
TENG, Q., D. R. EKMAN, T. W. COLLETTE, T. L. WHITEHEAD, G. T. ANKLEY, K. M. JENSEN, M. D. KAHL, AND D. L. VILLENEUVE. CHARACTERIZATION OF METABOLITES IN SMALL FISH BIOFLUIDS AND TISSUES BY NMR SPECTROSCOPY. Presented at Society of Environmental Toxicology and Chemistry Annual Meeting, Montreal, QC, CANADA, November 05 - 09, 2006.
Impact/Purpose:
This task is divided into four major research areas: (1) Development of computational tools and databases for screening-level modeling of the environmental fate of organic chemicals; (2) Metabolism of xenobiotics: Enhancing the development of a metabolic simulator; (3) Metabonomics: The use of advanced analytical tools to identify toxicity pathways; and (4) Software infrastructure to support development and application of transformation/metabolic simulators.
For many chemicals, multiple transformation/metabolic pathways can exist. Consequently, transformation/metabolic simulators must utilize transformation rate data for prioritization of competing pathways. The prioritization process thus requires the integration of reliable rate data. When this data is absent, it is necessary to generate a database with metabolic and transformation rate constants based on: (1) experimentally measured values, including those requiring the use of advanced analytical techniques for measuring metabolic rate constants in vivo and in vitro; (2) rate constants derived from SPARC and mechanistic-based QSAR models; and (3) data mined from the literature and Program Office CBI. A long-term goal of this project is to build this database. This information will be used to enhance the predictive capabilities of the transformation/metabolic simulators. As indicated previously, exposure genomics, which provide early signs of chemical exposure based on changes in gene expression, will be used to guide chemical fate and metabolism studies. The incorporation of exposure genomics into fate studies will provide information concerning (1) the minimal concentrations at which biological events occur; and (2) the identification of biologically relevant chemicals(s) in mixtures.
The capability of categorizing chemicals and their metabolites based on toxicity pathway is imperative to the success of the CompTox Research Program. Metabonomics, which is the multi-parametric measurement of metabolites in living systems due to physiological stimuli and/or genetic modification, provides such a capability. The application of metabonomics to toxicity testing involves the elucidation of changes in metabolic patterns associated with chemical toxicity based on the measurement of component profiles in biofluids, and enables the generation of spectral profiles for a wide range of endogenous metabolites. Metabolic profiles can provide a measure of the real outcome of potential changes as the result of xenobiotic exposure.
Description:
Nuclear magnetic resonance (NMR) spectroscopy has been utilized for assessing ecotoxicity in small fish models by means of metabolomics. Two fundamental challenges of NMR-based metabolomics are the detection limit and characterization of metabolites (or NMR resonance assignments) with limited sample mass. To face these challenges, we have begun a comprehensive NMR resonance assignment of metabolites observed in spectra of liver for two important small fish models - fathead minnow and zebrafish - and also for urine in male fathead minnow. Reported here are the results of the assignment using a suite of two-dimensional NMR spectroscopy, including TOCSY, 1H/13C HMBC, 1H/13C HMQC and HR MAS spectra acquired on two 600 MHz NMR systems equipped with LC/NMR/MS and cryogenic probe at the EPA NMR facility in Athens, GA and a 800 MHz system at the University of Georgia. In addition, we will report on the identity of metabolites in these tissues and fluids that seem to be most related to exposure to important endocrine disrupting chemicals.