We assessed the effects of cyclopenta[c]phenanthrene (CP[c]Ph) and benzo[a]pyrene (B[a]P; positive control) on CYP1A gene expression in brain of juvenile rainbow trout (Oncorhynchus mykiss) using the quantitative reverse transcription polymerase chain reaction (Q-RT-PCR). A group of hatchery raised rainbow trout, with an average body mass of 49.4 g and total length of 15.5 cm were given an intraperitoneal injection (10 mg*kg-1) of either CP[c]Ph or B[a]P in corn oil (2 mg*mi-1 corn oil) or corn oil alone (control). After 24 and 48 h, trout brains were collected for mRNA isolation and analysis. After 24 hours of the exposure, only B[a]P-treated rainbow trout had 10-fold higher number of CYP1A transcripts (mean = 3.63*106 transcripts*µg-1 total RNA) than control fish (3.24*105 transcripts*µg-1 total RNA; Tukey test, P<0.05). After 48 hrs, significantly higher levels of CYP1A expression (Tukey test, P<0.001) were found in either CP[c]Ph- or B[a]P- induced group (1.45*106 and 6.92*106 transcriptsźµg-1 total RNA, respectively) over a control group (mean=1.41*105 transcripts*µg-1 total RNA). The finding that CYP1A in brain tissue was inducible by CP[c]Ph, a polycyclic aromatic hydrocarbon (PAH) of different than B[a]P planar characteristics, may further validate the use of rainbow trout brain CYP1A mRNA levels as a biomarker of PAH exposure
