|Institution:||Oregon State University|
|Keywords:||zebrafish; Polycyclic aromatic hydrocarbons Toxicology|
|Full text PDF:||http://hdl.handle.net/1957/60687|
Polycyclic aromatic hydrocarbons (PAHs) are among the most widely known and studied environmental contaminants, originating from a range of natural and anthropogenic sources. PAHs are known to occur in the environment as complex mixtures, containing both unsubstituted PAHs, as well as a range of PAH derivatives. Among the less-studied of these derivative PAH classes are nitrated PAHs (NPAHs). NPAHs are known to form from atmospheric reactions with PAHs and can be found in the environment in a variety of matrices. Many NPAHs are known to be mutagenic, in some cases more so than the corresponding unsubstituted PAH. Less is known about the toxicity of NPAHs in whole-animal systems and for non-cancer endpoints, in particular with regard to the developmental toxicity and metabolism across a wide number of NPAH compounds, in a consistent model system. One of the major challenges in studying PAHs, and related compounds, is the high hydrophobicity and low water solubility of these compounds, which can result in losses due to partitioning of the analytes out of the aqueous phase and on to the walls of the container or exposure vessel. Numerous in vitro and in vivo models utilize plastic plates as exposure vessels, including the use of polystyrene 96-well plates for developmental toxicity testing in the developing zebrafish (Danio rerio) model. We directly measured the losses which occur due to sorption to the polystyrene plates during zebrafish testing for a set of PAHs and NPAHs. Sorptive losses in some instances were greater than fifty percent, in particular for the lower of the two exposure concentrations tested. These sorptive losses decrease the concentration of chemical available to the zebrafish embryos, and therefore impact the interpretation of dose-response toxicity data. In an attempt to create a predictive model for sorptive losses, the measured sorption was modeled against the log K[subscript ow], molecular weight, and subcooled liquid solubilities of the corresponding compounds. The correlations between subcooled liquid solubility and PAH sorption was statistically significant (p<0.05) for both concentrations tested, as well as molecular weight at the higher concentrations tested. However, none of the correlations were statistically significant for NPAH sorption, indicating a need for increased research in this area.We utilized the developing zebrafish model to investigate the developmental toxicity, and potential contributing mechanisms of action, of a suite of 27 NPAHs, as well as 10 heterocyclic PAHs (HPAHs) and 2 amino-PAHs (potential metabolites of NPAHs). Results from the toxicity screen indicate that NPAHs and HPAHs have a wide range of bioactivities in the developing zebrafish, from non-toxic at the concentrations tested to acutely toxic at sub-micromolar exposure concentrations. Activation of the aryl hydrocarbon receptor (AHR) pathway was investigated using a transgenic reporter zebrafish line and morpholino oligonucleotide knockdown to isolate specific isoforms of the AHR. The compoundsAdvisors/Committee Members: Simonich, Staci L. M. (advisor), Field, Jennifer (committee member).