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IP02 Wildlife Toxicology
(IP15) CYP1A1 expression as a biomarker of exposure in cetaceans: significance and limitations.
Godard, Celine1, 2, Clark, Rebecca2, Harper, Caroline3, Luo, Yang1, Moore, Michael1, Mesnick, Sarah4, Payne, Roger2, Rubio, Nadia5, Said, Maya6, Stegeman, John1, 1 Woods Hole Oceanographic Institution, Woods Hole, MA, USA2 Ocean Alliance, Lincoln, MA, USA3 University of North Carolina at Wilmington, Wilmington, NC, USA4 Southwest Fisheries Science Center, NMFS, La Jolla, CA, USA5 Centro de Investigaciones Biologicas del Noroeste, La Paz, Baja California Sur, Mexico6 Massachusetts Intitute of Technology, Cambridge, MA, USA
ABSTRACT- The cytochrome P450 1A1 (CYP1A1) is well characterized in many vertebrates and its induction is a robust biomarker of exposure to contaminants. However, knowledge of CYP1A1 in cetaceans is still limited, due in part to legal and logistical restrictions associated with tissue sampling. Skin biopsies are the principal type of samples that can be obtain from live cetaceans. We have detected CYP1A1 expression in biopsies from various cetacean species using immunohistochemistry (protein levels), catalytic activity (EROD) and semi-quantitative RT-PCR (mRNA levels). We have addressed three important limitations in interpreting CYP1A1 expression in cetacean biopsies. First, the dose-dependent characteristics of CYP1A1 in cetaceans need to be established. To that effect, we reviewed the advantages and limitations of a biopsy slice dosing assay that we recently developed. Second, various factors (sex, age, trophic level and type of prey, habitat, etc) besides contaminant exposure may affect CYP1A1 expression. To address this problem, we have refined a protocol for biopsy sub-sampling, which maximizes the scientific information that can be gathered from each biopsy (genetics; CYP1A1 mRNA, protein and catalytic levels; contaminant burden; stable isotope and fatty acid analyses). Third, in terrestrial mammals, another cytochrome P450 1 enzyme, CYP1B1, has been shown to play an essential role in xenobiotic metabolism as well as in xenobiotic and estrogen-induced carcinogenesis. In order to gather a more complete understanding of CYP1 enzymes expression in cetaceans, we measured both CYP1A1 and CYP1B1 levels in biopsies of several dolphin species using semi-quantitative RT-PCR. Results suggest higher levels of CYP1B1 than CYP1A1, stressing the importance to study both enzymes.
Key words: cetacean, CYP1A1, CYP1B1, marine mammals
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