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Project ID: 2004KY41B

Title: Linking chemical tolerance to reproductive resilience: CYP1A as a metric for predicting fish species distributions in chemically impacted habitats

Project Type: Research

Focus Categories: Toxic Substances, Water Quality, Ecology

Keywords: PCBs, monitoring, endocrine disruptors, bioindicators

Start Date: 03/01/2004

End Date: 02/28/2005

Federal Funds: $6,750

Non-Federal Matching Funds: $13,503

Congressional District: 6th

Principal Investigator:
Adria Elskus


Many of the pollutants present in our waterbodies today exert sublethal effects with far-reaching impacts on future generations. Polychlorinated biphenyls (PCBs) are ubiquitous aquatic pollutants with significant sublethal effects in both humans and fish, including altered reproduction, hormone disruption, immunosuppression and carcinogenesis. Significant levels of environmental PCBs in Kentucky have led to the posting of fish advisories in several Kentucky waterways (Kentucky Division of Water). The focus of the present study is the Town Branch-Mud River (TB/MR) system in Southwestern Kentucky, a PCB-contaminated area currently undergoing remediation. This proposal addresses several needs including the need to understand the impact of contaminants on higher organisms, to monitor the time course of recovery following contamination, and to evaluate the effectiveness of management efforts to improve water quality. PCBs are potent disruptors of reproductive function in fish. Although we and others have demonstrated that fish can develop resistance to some deleterious effects of PCBs, whether this resistance protects them from PCB-mediated reproductive toxicity is not known. Results of our previous USGS-funded research (O1HQGR0133) demonstrate that several resident fish species in the TB/MR system (Logan County, KY) have developed resistance to PCBs as evidenced by suppressed inducibility of the pollutant-inducible enzyme, CYP1A [9], likely in response to the extraordinarily high PCB concentrations present in this waterway, despite extensive remediation [13]. We propose to extend these studies to determine whether development of PCB-resistance has altered reproductive function in resident Town Branch fish. We hypothesize that there is a mechanistic link between resistance to PCB mediated induction of CYP1A and resistance to the deleterious effects of PCBs on reproductive function. Our objectives are to determine 1) if PCB-resistant resident populations in Town Branch have altered reproductive function compared to non-resistant populations of the same and different species, 2) whether species abundance reflects species-specific ability to develop resistance, and 3) whether altered regulation of the pollutant-metabolizing enzyme, CYP1A (a defining characteristic of PCB-resistance in fish) is mechanistically linked to reproductive function. Blocking CYP1A activity in fish blocks PCB effects on reproductive hormones [32], indicating a link between CYP1A, PCBs and reproductive function. We propose to use modulations in the biomarker, CYP1A, in conjunction with measures of reproductive success and species abundance, to evaluate population-level effects of contaminants in a PCB-contaminated stream, Town Branch, in Logan County, Kentucky. To evaluate reproductive function in adult resident fish, we will collect spawning resistant (yellow bullheads) and non-resistant (creek chub) fish from PCB contaminated and reference sites in Town Branch, populations we have characterized in previous studies [9, 13]. We will measure gonadosomatic index, plasma levels of sex steroids and vitellogenin (egg-yolk precursor protein), fecundity, fertilization success, hatch success, and hepatic CYP1A expression. To relate species abundance to chemical resistance, we will compare population abundance of resistant and non-resistant resident fish species in reference and contaminated Town Branch sites using established methods [35, 45, 53]. To evaluate the mechanistic role of PCBs and CYP1A in reproductive function, we will test the ability of CYP1A to modify PCB effects on an essential reproductive function, the ability of fish liver cells to synthesize the egg yolk precursor protein, vitellogenin. Regulation of vitellogenin synthesis is an extraordinarily sensitive indicator of reproductive function in fish [2]. By evaluating possible mechanistic links among resistance, reproductive function and population abundance, this study will provide insights into population-level consequences of acquired chemical resistance.

Progress/Completion Report PDF

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