Evaluation of the separate and joint effects of PAH and PCB contaminants on Atlantic tomcod Cytochrome 1A1 (CYP1A1) and Cytochrome 19A (CYP19A) genes

Toxicological effects of pollutants in aquatic ecosystems lead to the deterioration of water quality and adversely affect fish and human health. Hepatic CYP1A and ovarian CYP19A are recognized as useful biomarkers of exposure of fish to environmental contaminants such as polycyclic aromatic hydrocarbons (PAHs) and halogenated polychlorinated biphenyls (PCBs). Many studies have shown that levels of hepatic CYPlA mRNA in Atlantic tomcod (Microgradus tomcod) are increased by PCBs, but not by PAHs. However, the influence of PAHs on the response to PCBs have not previously been evaluated. In this study, quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR)has been used to measure the levels of liver CYP1A and ovarian CYP19A mRNAs in Atlantic tomcod exposed to PCB, PAH and both. Primers for CYP1A were based on the published sequence (FJ215063). Degenerate primers were designed for CYP19A based on the sequences for Cyprinus carpio (EU 375455), Milgil cephalus (AR859425, NG_007992, DT605703) and Gadus morhua (DQ402372). Using these, a partial sequence of tomcod aromatase was amplified and sequenced for specific primer design as well as production of in vitro transcripts. CYP1A and CYP19A mRNA levels were determined by Q-RT-PCR using the designed primers. CYP1A and CYP19A in vitro transcripts were used to provide quantitation and levels of AHNT1 and â-actin mRNA for normalization.