| Evidence of Spatially Extensive Resistance to PCBs in an Anadromous Fish of the Hudson River Zhanpeng Yuan,1 Simon Courtenay,2 R. Christopher Chambers,3 and Isaac Wirgin1 1Department of Environmental Medicine, New York University School of Medicine, Tuxedo, New York, USA; 2Department of Fisheries and Oceans, Gulf Region, Canadian Rivers Institute/Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada; 3Howard Marine Sciences Laboratory, Northeast Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, Highlands, New Jersey, USA Abstract
Populations of organisms that are chronically exposed to high levels of chemical contaminants may not suffer the same sublethal or lethal effects as naive populations, a phenomenon called resistance. Atlantic tomcod ( Microgadus tomcod ) from the Hudson River, New York, are exposed to high concentrations of polycyclic aromatic hydrocarbons (PAHs) and bioaccumulate polychlorinated biphenyls (PCBs) , polychlorinated dibenzo- p -dioxins (PCDDs) , and polychlorinated dibenzofurans (PCDFs) . They have developed resistance to PCBs and PCDDs but not to PAHs. Resistance is largely heritable and manifests at early-life-stage toxic end points and in inducibility of cytochrome P4501A (CYP1A) mRNA expression. Because CYP1A induction is activated by the aryl hydrocarbon receptor (AHR) pathway, as are most toxic responses to these compounds, we sought to determine the geographic extent of resistance to CYP1A mRNA induction by PCBs in the Hudson River tomcod population. Samples of young-of-the-year tomcod were collected from seven locales in the Hudson River, extending from the Battery at river mile 1 (RM 1) to RM 90, and from the Miramichi River, New Brunswick, Canada. Laboratory-reared offspring of tomcod adults from Newark Bay, in the western portion of the Hudson River estuary, were also used in this study. Fish were partially depurated in clean water and intraperitoneally injected with 10 ppm coplanar PCB-77, 10 ppm benzo[ a ]pyrene (BaP) , or corn oil vehicle, and levels of CYP1A mRNA were determined. CYP1A was significantly inducible by treatment with BaP in tomcod from the Miramichi River, from laboratory-spawned offspring of Newark Bay origin, and from all Hudson River sites spanning 90 miles of river. In contrast, only tomcod from the Miramichi River displayed significantly induced CYP1A mRNA expression when treated with PCB-77. Our results suggest that the population of tomcod from throughout the Hudson River estuary has developed resistance to CYP1A inducibility and probably other toxicities mediated by the AHR pathway. Tomcod from the Hudson River may represent the most geographically expansive population of vertebrates with resistance to chemical pollutants that has been characterized. Keywords: AHR, Atlantic tomcod, CYP1A, evolutionary change, genetic adaptation, Hudson River, PCBs, resistance. Environ Health Perspect 114:77-84 (2006) . doi:10.1289/ehp.8255 available via http://dx.doi.org/ [Online 21 September 2005]
Address correspondence to I. Wirgin, Department of Environmental Medicine, New York University School of Medicine, 57 Old Forge Rd., Tuxedo, NY 10987 USA. Telephone: (845) 731-3548. Fax: (845) 351-5472. E-mail: Wirgin@env.med.nyu.edu This study was supported by the Superfund Basic Research Program (grant ES10344) , a National Institute of Environmental Health Sciences Center grant (ES00260) , the Hudson River Foundation, and the Northeast Fisheries Science Center of the National Oceanic and Atmospheric Administration Fisheries Service. The authors declare they have no competing financial interests. Received 26 April 2005 ; accepted 21 September 2005.
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