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UBC Theses and Dissertations

Effects of nonylphenol on stress response in Rainbow Trout, Oncorhynchus mykiss Suto, Akiko


During the last few decades, there has been a great concern about the impact of endocrine disrupting chemicals (EDCs) on the health of wildlife and human populations. Nonylphenol, a degraded product of a widely used surfactant, has recently been identified as an estrogenic EDC. A set of experiments were conducted to examine how exposure to three levels (4, 20, and lOOppb) of nonylphenol for certain periods (1-3 weeks) affected physiological function in rainbow trout over time, in terms of their response to an acute stress of air exposure. It was shown that a high level (lOOppb) of nonylphenol suppresses the elevation of plasma Cortisol level in rainbow trout in response to the acute stress of air exposure. In addition, the fish treated with nonylphenol were incapable of reducing their Cortisol levels back to pre-stress levels after 24 hours. The normal response of plasma glucose levels to the stress was observed. Plasma levels of thyroid hormones decreased significantly (p<0.0\) after exposure to the high level of nonylphenol for 3 weeks. Nitrite, a toxic chemical naturally present in the aquatic environment, was used in the experiment for comparison and had no effect on the normal stress response of Cortisol. The results from these experiments suggest that nonylphenol may have negative impacts on fish, such as a lower chance of survival and vulnerability to diseases, by interfering with normal function of the endocrine system.

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