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ToxSci Advance Access published online on March 14, 2006
Toxicological Sciences, doi:10.1093/toxsci/kfj154
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© The Author 2006. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Received November 28, 2005
Accepted February 10, 2006

Environmental Toxicology

Fasting Augments PCB Impact on Liver Metabolism in Anadromous Arctic Charr

Mathilakath M. Vijayan 1 *, Neelakanteswar Aluru 1, Alec G. Maule 2, and Even H. Jørgensen 3

1 Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
2 USGS-BRD, WFRC, Columbia River Research Laboratory, Cook, Washington, USA
3 Norwegian College of Fishery Science, University of Tromsø, Tromsø, Norway

* To whom correspondence should be addressed.
Mathilakath M. Vijayan, E-mail: mvijayan{at}uwaterloo.ca


  Abstract

Anadromous Arctic charr (Salvelinus alpinus) undertake short feeding migrations to seawater every summer and accumulates lipids, while the rest of the year is spent in fresh water where the accumulated lipid reserves are mobilized. We tested the hypothesis that winter fasting, and the associated polychlorinated biphenyls (PCBs) redistribution from lipid depots to critical tissues impairs the liver metabolic capacity in these animals. Charr were administered Aroclor 1254 (0, 1, 10 and 100 mg /kg body mass) orally and maintained for 4 months without feeding to mimic seasonal winter fasting, while fed groups (0 and 100 mg Aroclor 1254/ kg) were maintained for comparison. A clear dose-related increase in PCB accumulation and CYP1A protein content were observed in the livers of fasted fish. This PCB concentration and CYP1A response with the high dose of Aroclor were 1.5-fold and 3-fold greater in the fasted than in the fed fish, respectively. In fed fish, PCB exposure lowered liver glycogen content, whereas none of the other metabolic indicators were significantly affected. In fasted fish, PCB exposure depressed liver glycogen content and activities of glucose-6-phosphate dehydrogenase, alanine aminotransferase, lactate dehydrogenase and phosphoenolpyruvate carboxykinase, and elevated 3-hydoxyacylcoA dehydrogenase activity and glucocorticoid receptor protein expression. There were no significant impacts of PCB on hsp70 and hsp90 protein contents in either fed or fasted fish. Collectively, our study demonstrates that winter emaciation associated with the anadromous lifestyle predisposes Arctic charr to PCB impact on hepatic metabolism, including disruption of the adaptive metabolic responses to extended fasting.

Keywords: Salvelinus alpinus; Aroclor 1254; CYP1A; glucocorticoid receptor; hsps; gluconeogenesis.
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