Laboratory characterization and ecological applications of five inducible gene biomarkers of toxicant exposure in rainbow trout (Onchor. mykiss)

One objective of this dissertation was characterization of the effect of three chemicals (benzo[a]pyrene (BaP), estradiol, and cadmium) on a suite of five inducible gene biomarkers (CYP1A1, metallothionein (MT), vitellogenin (Vtg), activin, and multiple xenobiotic resistance (MXR)). Chemical exposure to rainbow trout (RBT) to single chemicals and binary and trinary mixtures highlighted the sensitivity of biomarkers to low, sub-lethal levels of xenobiotic chemicals. The 48 hr exposure to BaP and estradiol produced significant increases in CYP1A1 and Vtg, respectively. Activin and MXR showed significant suppression in response to estradiol, and MT showed only small changes in response to any chemical. Only CYP1A1 was shown to respond to a model inducer (BaP) in a concentration dependent manner.; The second objective was application of biomarkers by characterizing expression in fish exposed in situ to water under natural field conditions. The first application was exposure of RBT to two streams in Ohio known to contain a mixture of contaminants that were expected to affect expression of the biomarkers. Results from an 8-day and 48 hr trial exposure indicated that (1) biomarkers were significantly induced or suppressed within 48 hr, (2) biomarkers were able to indicate the presence of specific contaminants, and (3) there were significant changes in biomarker expression depending on the initial water conditions in which fish were reared. The second application was in situ exposure of laboratory-reared fish to lakes in the Sierra Nevada alpine region of Nevada and California. Biomarkers were tested for their ability to supplement a multi-level, ecosystem evaluation of water and overall lake habitat quality. Results of a sixteen lake site survey suggest that RBT biomarkers indicated specific contaminant contact and that the biomarker CYP1A1 was associated with varying levels of motorized watercraft activity. The final objective of the dissertation was evaluation of the MT biomarker as a sentinel of accumulated physiological damage and potential death in response to stress associated with over-wintering changes in temperature in juvenile RBT. Results suggested that minimally lethal levels of cadmium could positively induce MT and that a reduction in temperature was protective against mortality compared to normal maintenance temperatures, contradicting a predicted response at reduced temperatures. (Abstract shortened by UMI.)...