| Benzo(a)Pyrene (B(a)P) is a typical representative of PAHs which are the organic chemicals to be carcinogenic and mutagenic to animals and human. In order to assess B(a)P biological effect on the marine fish, DNA damages in cells, EROD activities and P4501A1 mRNA expression in the liver of red seabream Pagrus major exposed to B(a)P were studied using molecular techniques and comet assay. The relationship among blood cell DNA damages, liver P4501A1 mRNA expression and EROD activities were analyzed and the result showed as following:1. The cDNA and the genomic DNA sequences of P4501A1 were cloned from the liver RNA of the red seabream. Similarity analysis indicated that P4501A1 gene amplified from the red seabream raised in China was homologous to of other reported P4501A1 genes.2. The DNA damage in red seabream, which were divided into several groups exposed to three B(a)P concentrations (0.8μg/L,1.4μg/L and 2.0μg/L) was determined by comet assay. Results showed: that the DNA damage level was increasing during 4-24 h and decreased rapidly to the control level at 96 h. In the study, the electrophoresis conditions of comet assay were optimized for great amounts of samples, the single LMA on the cover of cell culture plate was better in respect of convenience, time-saving and fixing gel than the'sandwich'on frosted microscope slides. The positive correlations between tail length, the ratio of tail length and head length, tail moment and TDNA were observed and the index could fit reality of DNA damage.3. After exposed to different concentrations (0.8μg/L,1.4μg/L and 2.0μg/L) of B(a)P, the liver EROD activities of three groups of red seabream were all significantly induced. With the time passing, the liver EROD activities increased and was up to the peak at 24h, then decreased gradually and was down to the control level at 98 h. A good dose - response relationship between liver EROD activities and B(a)P concentrations.was observed at 4 h.
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