Date of Award

2014

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Biological Sciences

Keywords

Biological sciences, Adaptation, Brown bullhead, CyYP1A, Great lakes, P53, Pollution

Supervisor

Hubberstey, Andrew

Rights

info:eu-repo/semantics/openAccess

Abstract

Areas of the Great Lakes are classified as polluted and are inclusive of PAHs and PCBs, both of which are agonists of the aryl hydrocarbon receptor. To determine whether resident brown bullhead ( Ameiurus nebulosus ) populations have developed resistance to the genotoxic effects of these compounds, we measured population level differences in CYP1A and p53 expression in in fish from clean and contaminated sites. At the resting level, fish from polluted sites had lower CYP1A expression and high p53 expression. When fed 50mg/kg x3 doses of Benzo[a]pyrene treated food, p53 expression decreased in contaminated fish and increased in clean fish. Interestingly, though CYP1A expression increased initially in contaminated fish, after clearing, the CYP1A response decreased, potentially returning towards the low resting response observed. Similarities in responses between contaminated sites, which were different from fish from clean sites, suggested that p53 and CYP1A may be part of an evolved population-level response, contributing towards the resistance of bullhead living in polluted sites. To measure whether or not these responses were heritable, the response of farm-raised of F1 offspring was measured. The p53 and CYP1A response of clean and contaminated F1 offspring fish to BaP was similar to that of their wild-caught parents, suggesting that the heritable responses measured has a genetic component. When p53 and CYP1A expression in conjunction with EROD and GST activity was measured in clean and contaminated fish in response to clean and contaminated sediment, refractory CYP1A responses measured in acute fish was not persistent to cleared fish but was heritable to contaminated F1 offspring. Similarly, higher p53 expression in recovered cleared fish in response to contaminated sediment correlated to a high F1 p53 response. EROD activity measured between clean and contaminated fish in both experiments suggested an acclimatized response, but may be inclusive of other enzymes capable of EROD activity and not just CYP1A. GST expression did not reveal any significant differences in expression between populations. Results of this study imply that bullhead have evolved p53 and CYP1A responses as a population to resist the consequences of genotoxic stress in polluted sites.

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