CAGED AND WILD FISH - INDUCTION OF HEPATIC CYTOCHROME-P-450 (CYP1A1) AS AN ENVIRONMENTAL BIOMONITOR

Hepatic monooxygenase activity can be induced by many different enviro nmental chemical contaminants, and measurement of this activity has be en proposed as an environmental biomonitor. Using in situ caged catfis h and largemouth bass, and collected wild killifish, environmental ind uction of hepatic CYP1A1 was investigated using catalytic enzyme assay s, regiospecific metabolism, immunodetection, and nucleic acid hybridi zation. The purpose of these studies was to evaluate these techniques for detection of CYP1A1 induction as a potential environmental biomoni tor of environmental chemical contamination. Exposure of catfish in ca ges to polyaromatic hydrocarbon-(PAH-) and polychlorinated biphenyl- ( PCB-) contaminated river water for two, four, or six weeks resulted in fourfold increases in ethoxyresorufin-0-deethylase (EROD) activity an d three- and fivefold increases in immunoreactive CYP1A1 protein and h ybridizable CYP1A1 mRNA, respectively, when compared to laboratory wat er control values. Hybridizable CYP1A1 mRNA in caged largemouth bass i ncreased 5. 1-fold at 1 d of exposure. Caged largemouth bass had 5-, 1 .4-, and 0.8-fold increases at 3 d and 6-, 2.4-, 0.4-fold increases at 7 d of river water exposure in EROD, immunoreactive CYP1A1 protein, a nd CYP1A1 mRNA, respectively, when compared to laboratory water contro l values. Livers of killifish from a 2,3,7,8-tetrachlorodibenzo-p-diox in-contaminated area had threefold higher EROD activity and similarly elevated immunoreactive CYP1A1 protein, a two- to fourfold increase in CYP1A1 mRNA, and a four- to eightfold increase in 6beta-hydroxyproges terone activity, when compared to killifish livers sampled from a ''cl ean'' site. These results indicate that catalytic activity measurement s, immunodetection, and nucleic acid hybridization may be used to dete ct environmental hepatic CYP1A1 induction in fish, and may be useful f or the biomonitoring or screening of selected environments for chemica l contamination.