Hepatic phase I and II biotransformation responses and contaminant exposure in long-finned pilot whales from the Northeastern Atlantic

Faroe Island pilot whales have been documented to have high body burdens of organohalogen contaminants (OHCs), including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), but low burdens of their respective hydroxylated metabolites (OH-PCBs and OH-PBDEs). The present study investigated the hepatic expression and/or catalytic activities of phase I and II biotransformation enzymes in relation to hepatic concentrations of target OHCs, including OH-PCBs and OH-PBDEs, in long-finned pilot whales (Globicephala melas) from the Northeastern Atlantic. CYP1A, 2B, 2E and 3A protein expressions were identified in juveniles and adult males, but not in adult females. Ethoxyresorufin-O-deethylase (EROD) activity was significantly lower in adult females than in juveniles and adult males. Using multivariate analyses to investigate relationships between biological responses and OHC concentrations, a positive relationship was identified between EROD and OHCs. The activity levels of phase II conjugating enzymes (uridine 5'-diphospho-glucuronosyltransferase [UDPGT], and glutathione S-transferase [GST]) were low. The analyses of mRNA expression did not show correlative relationships with OHC concentrations, but cyp1a and ahr transcripts were positively correlated with EROD activity. We suggest that the low concentrations of OH-PCBs and OH-PBDEs reported in pilot whales is probably due to the identified low phase I biotransformation activities in the species.