title: Postmortem stability of brain GABAergic and glutamatergic receptors and enzymes under ecological conditions.
abstract: Neurochemical biomarkers have emerged as useful tools for assessing the subclinical neurological impacts of environmental toxicants in birds and other wildlife. Careful consideration of biomarker stability is necessary before implementing their use on tissues from ecological studies, as receptors and enzymes in the brain may be affected by postmortem conditions. The goal of this study was to evaluate the postmortem stability of key GABAergic and glutamatergic receptors (N-methyl-D-aspartate (NMDA), gamma-aminobutyric acid (GABAA-benzodiazepine)) and enzymes (glutamine synthetase (GS), glutamic acid decarboxylase (GAD)) under environmentally relevant field and storage conditions to determine their suitability as biomarkers. We exposed chicken embryo brains to postmortem environmental and storage conditions typical for ecological studies (12, 24, and 48 h at 7 °C or 25 °C; 1, 4, and 8 weeks at -80 °C or -20 °C; 1 or 2 freeze thaw cycles), and measured [3H] MK-801 binding to the NMDA receptor, [3H] flunitrazipam binding to the GABAA-benzodiazepine receptor, GS activity, and GAD activity. We found that [3H] MK-801 binding is stable under all conditions studied. GAD activity was fairly stable under each storage and environmental temperatures for all durations, but was significantly less stable when stored at -20 °C than at -80 °C. [3H] flunitrazipam binding and GS activity were both impacted by environmental and storage temperature and duration, and might best be utilized in studies of samples with similar histories. Our findings here demonstrate that caution is warranted when comparing samples with different collection and storage histories, but that some biomarkers are fairly stable under various conditions.
authors: Department of Environmental Health Sciences, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA.
authors: Jennifer
authors: J
authors: Rutkiewicz
authors: Niladri
authors: N
authors: Basu
mesh_terms: D000818:Animals; D001569:Benzodiazepines / Q000378:metabolism; D015415:Biomarkers / Q000737:chemistry*; D001921:Brain / Q000201:enzymology* / Q000378:metabolism; D002642:Chick Embryo; D016291:Dizocilpine Maleate / Q000378:metabolism; D004777:Environment; D004784:Environmental Monitoring / Q000592:standards; D005968:Glutamate Decarboxylase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D011963:Receptors, GABA-A / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D015183:Restriction Mapping; D013696:Temperature; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D015415:Biomarkers; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; D001569:Benzodiazepines; D005680:gamma-Aminobutyric Acid; D016291:Dizocilpine Maleate; D005968:Glutamate Decarboxylase; D005974:Glutamate-Ammonia Ligase