PM16 Molecular Indicators for Ecological Exposure
Exhibit Hall
8:00 AM - Monday
(PM271) Antioxidant transcriptional markers in field-exposed rainbow trout.
Marwood, C1, Oris, J2, 1 University of California Santa Barbara, Santa Barbara, CA, U.S.A.2 Miami University, Oxford, OH, U.S.A.
ABSTRACT- Cellular toxicity of many environmental contaminants occurs via generation of reactive oxygen species, with subsequent damage to lipids, enzymes and DNA. Polycyclic aromatic hydrocarbons (PAHs), produced by two-stroke engines in watercraft, are common contaminants in surface waters causing oxidative stress in aquatic organisms. The typical cellular response to oxidative stress is modulation of antioxidant enzymes, such as glutathione S-transferase, glutathione peroxidase, and superoxide dismutase. Changes in the activity of these enzymes have been proposed as biomarkers of exposure to contaminants that cause oxidative stress, but results of field exposures using these assays have been inconsistent. Transcriptional markers, based on quantification of enzyme mRNA levels rather than enzyme activity, are capable of rapid detection of oxidative stress in fish exposed to contaminants in the laboratory. To test this system under field conditions, the modulation of antioxidant mRNA transcripts was examined in hatchery rainbow trout caged in several Sierra Nevada lakes. Lakes were classified from low- to high-impact, according to several criteria such as boat traffic, land use, water quality, and contamination with PAHs. Transcript levels of several antioxidant enzymes in both liver and gill varied considerably between lakes (6-fold), but the response was not consistent with aqueous PAH concentrations or apparent human impact levels. Similar to the enzyme activity measured in previous field exposures, transcript levels were highly variable, and apparently reflect a response to multiple sources of oxidative stress, not just chemical contaminants.
Key words: biomarker, PAHs, transcript, antioxidant