title: Gill EROD in monitoring of CYP1A inducers in fish: a study in rainbow trout (Oncorhynchus mykiss) caged in Stockholm and Uppsala waters.
abstract: The gill filament 7-ethoxyresorufin O-deethylase (EROD) assay was evaluated as a monitoring tool for waterborne cytochrome P4501A (CYP1A) inducers using rainbow trout (Oncorhynchus mykiss) caged in urban area waters in Sweden. To compare the CYP1A induction response in different tissues, EROD activity was also analyzed in liver and kidney microsomes. Immunohistochemistry was used to localize CYP1A protein in gill and kidney. In two separate experiments fish were caged at sites with fairly high expected polyaromatic hydrocarbon (PAH) contamination. In the first experiment, gill EROD activities were analyzed in fish exposed for 1-21 days in a river running through Uppsala. The reference site was upstream of Uppsala. In the second, gill, liver and kidney EROD activities were analyzed in fish exposed for 1-5 days in fresh or brackish waters of Stockholm and in a reference lake 60km north of Stockholm. Fish exposed for 5 days followed by 2 days of recovery in tap water in the laboratory were also examined. The gill consistently showed a higher EROD induction compared with the liver and the kidney. After 1 day of caging, gill EROD activity was markedly induced (6-17-fold) at all sites examined. Induction in gill was pronounced (5-7-fold) also in fish caged at the reference sites. In the 21-day exposure study gill EROD activity remained highly induced throughout the experiment (26-fold at most) and the induced CYP1A protein was exclusively confined to the gill secondary lamellae. In the 5-day exposure experiment, EROD activity peaked after 1 day and then declined in both gill and liver, while CYP1A immunostaining in the gill remained intense over the 5-day period. In the kidney, CYP1A staining was weak or absent. We conclude that gill EROD activity is a more sensitive biomarker of exposure to waterborne CYP1A inducers than EROD activity in liver and kidney.
authors.affiliation: Uppsala University, Department of Environmental Toxicology, Norbyvägen 18 A, SE-752 36, Uppsala, Sweden.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Abrahamson
authors.forename: Carin
authors.initials: C
authors.lastname: Andersson
authors.forename: Maria E
authors.initials: ME
authors.lastname: Jönsson
authors.forename: Oscar
authors.initials: O
authors.lastname: Fogelberg
authors.forename: Jan
authors.initials: J
authors.lastname: Orberg
authors.forename: Björn
authors.initials: B
authors.lastname: Brunström
authors.forename: Ingvar
authors.initials: I
authors.lastname: Brandt
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis / Q000096:biosynthesis*; D004784:Environmental Monitoring / Q000379:methods*; D004790:Enzyme Induction / Q000187:drug effects; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects*; D005880:Gills / Q000201:enzymology; D007150:Immunohistochemistry / Q000662:veterinary; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D017686:Oncorhynchus mykiss / Q000502:physiology*; D013548:Sweden; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*