Lack of CYP1A responsiveness in species inhabiting chronically contaminated habitats: two varieties of resistance?

Organisms chronically exposed to organic pollutants such as polychlorinated biphenyls (PCBs) can develop resistance to these chemicals, a condition associated with reduced inducibility of the biomarker enzyme cytochrome P450 1A (CYP1A). This study addresses the CYP1A response of members of the families Ictaluridae and Centrarchidae, two fish families found throughout much of the United States. We measured CYP1A expression, PCB body burdens, and conducted CYP1A challenge experiments in species from these families residing in the Town Branch/Mud River system (Logan County, KY, USA), a stream system historically contaminated with high levels of PCBs.

Differential sensitivity of CYP1A to 3,3',4',4-tetrachlorobiphenyl and benzo(a)pyrene in two Lepomis species.

Although Lepomis species are abundant in a wide variety of habitats throughout North America and could serve as potentially valuable biomonitoring tools, few studies have examined the induction of pollutant biomarkers in this genus. We hypothesized that the induction of cytochrome P-450 1A (CYP1A), a sensitive and widely used indicator of response to aquatic contaminants, would serve as an effective biomarker of organic pollutant exposure in Lepomis species. We examined the response of CYP1A and two of the major pollutant-responsive phase II enzymes, glutathione S-transferase (GST), and uridine diphosphate glucuronyltransferase (UDPGT), in Lepomis exposed to organic pollutants under laboratory and field conditions.

CYP1A expression in caged rainbow trout discriminates among sites with various degrees of polychlorinated biphenyl contamination.

It has become increasingly apparent that resident fish can develop resistance to chemicals in their environment, thus compromising their usefulness as sentinels of site-specific pollution. By using a stream system whose resident fish appear to have developed pollutant resistance (Brammell et al., Mar Environ Res 58:251-255, 2005), we tested the hypothesis that the pollutant-inducible biomarker, cytochrome P4501A (CYP1A), as measured in field-caged juvenile rainbow trout (Oncorhynchus mykiss), would reflect relative pollution differences between reference and polychlorinated biphenyl (PCB)-contaminated sites.

Apparent lack of CYP1A response to high PCB body burdens in fish from a chronically contaminated PCB site.

Chronic exposure to organic contaminants such as polychlorinated biphenyls (PCBs) can lead to the development of resistance to these chemicals, a condition associated with reduced response of CYP1A1, a pollutant-inducible biomarker. We measured CYP1A activity (ethoxyresorufin o-deethylase, EROD) and PCB concentrations in feral fish from the Town Branch/Mud River system (Logan County, KY), a stream historically contaminated with PCBs and partially remediated. As a first step in evaluating the possible development of resistant populations in this system, we measured CYP1A expression and PCB body burdens in resident fish from sites we previously characterized as containing biologically significant levels of CYP1A inducing compounds.