Environmental and contaminant influences on cardiorespiratory function and metabolism in fish

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Fish are facing increasing impacts not only from aquatic contaminants, but simultaneously also from thermal stresses due to global warming. Increasing our understanding of how these factors interact is critical for survival of fish species. There is a fundamental need for fish to be able to adjust cardiac, respiratory and metabolic function to meet environmental demands in order to obtain food, avoid predators, grow, reproduce and survive. Fish are exposed to persistent dioxins (a by-product of industrial processes and fires) or to rapidly degraded polycyclic aromatic hydrocarbons (PAHs) that come from oil spills, boat activity and urban run-off. These contaminants cause lethal cardiac defects if exposure occurs during a critical period of development in larval fish. However, they are also increasingly recognized to alter metabolism, cause cardiac arrhythmias and impair swimming in adult fish. The aryl hydrocarbon receptor (AhR) is a transcription factor receptor activated by certain dioxins and PAHs. AhR increases expression of many genes, including cytochrome P450 1A (CYP1A). Both AhR and CYP1A have been implicated in normal cardiac development via an unknown endogenous signal, while a similar endogenous role in metabolism is unknown. Moreover, recent evidence suggests epigenetic mechanisms may be involved in normal AhR-mediated signals when stimulated by dioxins or PAHs. Finally, both developmental and functional toxicity of PAHs have recently been hypothesized to involve inhibition of the inward delayed rectifier potassium current in fish cardiomyocytes. The proposed research will utilize state-of-the-art ultrasound biomicroscopy combined with swim tunnel respirometry to assess cardiorespiratory performance in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss) exposed to these contaminants in developmental and acute exposure scenarios. This will be combined with pharmacological, biochemical, molecular and whole cell channel recording techniques that will increase our understanding of the basic biological role of AhR, the mechanisms of dioxin and PAH toxicity as well as their interaction with thermal stress in fish. With better understanding of how toxicants and thermal stress interact, we can set better environmental regulations to protect our fisheries resources in Canada.**