Cytochrome P450 1A mRNA in the Gambusia affinis and Response to Several PAHs

Cytochrome P4501A (CYP1A) has been used as a specific biomarker for monitoring water contamination such as PAHs, PCBs and dioxins. In the present study, the cyp1a gene of Gambusia affinis was cloned and sequenced and their expressions under PAHs exposure were characterized. The newly identified cyp1a encodes a protein with 521 amino acids that shared 96-80% identity with other Cyprinodontiformes fishes. RT-PCR analysis revealed that the basal mRNA level of cyp1a was highly expressed in liver and intestine. The expression level of cyp1a was significantly induced by exposure to 100 μg/L 3, 4-Benzopyrene (BaP) for 5 days in the muscle, testis, brain, liver and intestine of adult male fish. Except in the testis, the induced mRNA level of cyp1a ultimately decreased after prolonging the exposure time to 25 days. As for testis, the induced mRNA level of cyp1a was maintained at a high level during the entire exposure time under 100 μg/L BaP exposure. Furthermore, the expression of cyp1a increased with exposure time under a relatively low exposure concentrations 1 μg/L. Regarding the effects of other PAHs, D(a,h)A, BbF, and BaA showed a statistically significant effect of induction on mRNA level of cyp1a in the muscle, testis, brain, liver and intestine.