MP7 Toxicogenomics in Environmental Studies
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(WAN-1117-816850) CYP1 mRNA expression in Fundulus and catfish following BaP Exposure.

Wang, L¹, Scheffler, B², Ford, A¹, Ganesan, S¹, Willett, K¹, ¹ University of Mississippi, University, MS, USA² USDA-ARS, Stoneville, MS, USA

ABSTRACT- While CYP1A has been recognized, studied and used as a biomarker in fish for many years, understanding of the significance of more recently cloned fish CYP1B and CYP1C genes is lacking. In mammals, CYP1B1 is responsible for activating polycyclic aromatic hydrocarbons, such as benzo(a)pyrene (BaP) and estradiol to carcinogenic intermediates. We have cloned full length and partial CYP1-like cDNAs from the channel catfish and Fundulus heteroclitus, respectively. The channel catfish CYP1B codes for a putative protein of 536 AA that shares the highest amino acid identity with carp 1B2 (68%). Fundulus partial cDNA was most similar to scup 1C1 (66%). Compared to mammals, the physiological significance, metabolic activities and inducers of teleost CYP1s apart from CYP1A are largely unknown. We found CYP1B mRNA was detectable in catfish gill, liver, gonad and blood and statistically significantly inducible by 20 mg/kg i.p. BaP exposure. In dose-response studies with catfish primary cultured gill cells, the tissue with the highest constitutive levels of CYP1B, BaP, TCDD, PCBs 77, 126, and 169 induced CYP1B message by 10-fold or more relative to DMSO controls. On-going studies are using Fundulus embryos to investigate the developmental expression of CYP1s following exposure to waterborne BaP (10 g/L) for the initial 10 days postfertilization. Our results suggest that teleost CYP1s, in addition to CYP1A, are inducible by AhR agonists, have a broad tissue distribution, and may be physiologically significant biomarkers of contaminant exposure.

Key words: Fundulus, catfish, CYP1B, BaP