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(498) Is cytochrome P450 1A a practical and effective biomarker of organochlorine exposure in marine mammals?
Miller, Kelsey*,1,2, Assuncao, Marta3, Dangerfield, Neil1, Bandiera, Stelvio2, Ross, Peter1, 1 Institute of Ocean Sciences, Sidney, BC, Canada2 University of British Columbia, Vancouver, BC, Canada3 Instituto de Ciencias Biomedicas Abel Salazar, Porto, Portugal
ABSTRACT- Organochlorines are known to accumulate in lipid stores of marine mammals and have been linked to reproductive, developmental, and immunological toxicities. Induction of cytochrome P450 1A (CYP1A) in liver is one of the most widely used biomarkers of organochlorine exposure in vertebrates. However, skin is often the only CYP-containing tissue that can be readily obtained from live, free-ranging cetaceans using non-invasive techniques. The objectives of this study were to determine whether samples collected using non-invasive methods (eg. skin) could be used to quantify CYP1A as a biomarker of contaminant exposure in marine mammals. We carried out a comparative inter-tissue study using liver (~30-100 mg) and skin/blubber (~150-250 mg) biopsies from 20 free-ranging harbour seal pups captured in southern British Columbia, Canada. Seals were temporarily held in captivity under veterinary care and were released following the collection of tissue samples. Additional skin/blubber biopsies were collected in the field from adult harbour seals in B.C. and pups in both B.C. and Washington State. CYP1A catalytic activity and protein levels were measured in S9 fractions by a fluorescence microplate ethoxyresorufin O-deethylase (EROD) assay and immunoblotting, respectively. EROD activity and two putative CYP1A protein bands were quantified in both liver and skin. Induction of CYP1A protein was observed in three seals after in vivo treatment with -naphthoflavone, a non-toxic inducer of CYP1A. EROD activity in both liver and skin increased during three weeks in captivity, possibly due to stress, diet, or age-related effects. Results suggest that contaminants induce CYP1A expression in liver, but more work is needed to assess the use of skin as a surrogate tissue. In order to optimize this biomarker approach, further research into other factors affecting CYP1A expression in marine mammals (eg. age, diet, sex, and condition) should also be carried out. We are currently applying the same techniques to analyze skin biopsies collected from free-ranging killer whales.
Key words: marine mammals, CYP1A, biomarkers, organochlorines
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