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(22-36) Stress protein expression and immunological responses in juvenile Chinook salmon (Oncorhynchus tshawytscha) exposed to pesticides. Eder, Kai1, Leutenegger, Christian1, Koehler, Heinz2, Werner, Inge*,1, 1 University of California, Davis, California, USA2 University of Tuebingen, Germany ABSTRACT- Pacific salmon species have declined at an alarming rate in the last 40 years. The decline may, in part, be due to increased exposure to environmental stressors. In the Sacramento-San Joaquin Delta, California, pesticides at concentrations toxic to aquatic invertebrates have been detected for a number of years during winter months, when juvenile Chinook salmon (Oncorhynchus tshawytscha) are migrating through. Although concentrations are below acutely toxic levels for salmon, there is concern that pesticides may be having deleterious sublethal effects. As the first part of an integrated laboratory and field study, we investigated several sublethal molecular and biochemical responses in hatchery raised juvenile Chinook salmon after exposing them to either the organophosphate chlorpyrifos or the pyrethroid esfenvalerate for a duration of 96 hours. Four to five month old salmon were exposed to a range of concentrations to determine acute toxicity, and tissue samples were analyzed for stress proteins (hsp60, hsp70, hsp90) and cytokine induction (IL-1b, TGF-b, IGF-1, Mx protein). Stress proteins are involved in cellular protein homeostasis and repair, and are induced by a variety of stressors. Cytokines are mediators of the immune system and may be indicative of immunotoxic effects. At the highest concentrations, both pesticides led to complete (100%) mortality of juvenile salmon, whereas medium and low concentrations resulted in high survival rates. Significant differences in stress protein expression were found between control and all surviving chlorpyrifos-exposed fish. We will compare these results with findings from our esfenvalerate experiment. Real-time PCR systems for the quantification of cytokine gene expression in kidney and spleen of Chinook salmon will be presented, and we will discuss our results on their induction patterns in response to pesticide exposure. Key words: chinook salmon, pesticides, stress proteins, cytokines |
