Differential expression of CYP1A1 mRNA in gill, intestine and liver of tilapia fed with PCB Aroclor-1254 and Aroclor-1260 spiked food.

The differential expression of cytochrome P4501A1 gene expression (CYP1A1) in liver, intestine and gill of juvenile tilapia following oral exposure to polychlorinated biphenyl (PCB) Aroclor-1254 or Aroclor-1260 spiked food were investigated. The fish was fed with 0.1 g/g of body weight each day of the spiked food with a concentration of approximately 8 ppm. Fish fed with betaNF- or acetone-spiked food were used as positive and negative controls, respectively. On day 1, 3 and 7 of post-treatment, the fish were sampled and analyzed for the total accumulated levels of PCBs, as well as the induced levels of CYP1A1 mRNA. Our results indicated that the fish fed with PCBs-spiked food showed a time-dependent bioaccumulation of PCBs. The time course studies also revealed that in the first 3 days of feeding, significant increases in CYP1A1 were found in intestine (betaNF: 320% and Aroclor-1260: 290%), followed by liver (betaNF: 144%, Aroclor-1260: 123% and Aroclor-1254: 110%). The transcript levels, then declined slowly. There was no induction of gill CYP1A1 mRNA expression in all treatment groups. Among all the tested tissues, the highest intestinal CYP1A1 transcripts induction has highlighted its prompt response to dietary PCBs exposure. Our study supported the important role of intestine in response to dietary PCBs exposure. In addition, in the present study the relative potency of Aroclor-1260 over Aroclor-1254 in stimulating CYP1A1 expression was discussed, indicating that the highly chlorinated PCBs had a higher potency of bioaccumulation and CYP1A1 mRNA induction.