Amnesic shellfish poisoning toxin stimulates the transcription of CYP1A possibly through AHR and ARNT in the liver of red sea bream Pagrus major

To investigate the role of detoxification-related liver genes in amnesic shellfish poisoning toxin metabolism, red sea bream Pagrus major were exposed to domoic acid (DA, 2 μg g−1 wet weight) for 24 h. Hepatic mRNA expression levels of AHR, ARNT, CYP1 and GSTs were determined by semi-quantitative RT-PCR. The cytosolic factors aryl hydrocarbon receptor (AHR) and aryl hydrocarbon receptor nuclear translocator (ARNT) mRNA levels of DA exposure group were substantially enhanced by 113.3% and 90.9%, respectively. Consistent with this result, the phase I xenobiotic metabolizing enzyme (XME) cytochrome P-450 1A (CYP1A) was significantly induced. In contrast, the transcriptions of three major phase II XME glutathione S-transferases as well as heat shock protein 70 were not significantly affected by DA exposure. These results suggest a possible role of CYP1A after DA exposure in the toxin metabolism of marine fish, possibly through the AHR/ARNT signaling pathway.