title: Impact of humic substances on EROD activity in gill and liver of three-spined sticklebacks (Gasterosteus aculeatus).
abstract: Humic substances (HS) are ubiquitous in the environment and have been found to influence physiological functions of aquatic organisms. In the present study, three-spined sticklebacks (Gasterosteus aculeatus) were exposed to HS of different origins to evaluate effects on the 7-ethoxyresorufin O-deethylase (EROD) activity catalyzed by cytochrome P4501A (CYP1A) in the liver and the gill. To that end, three-spined sticklebacks were exposed for 48 h to different concentrations of synthetic humic acid (AHA), Nordic reservoir natural organic matter (N.R.-NOM) and water from six lakes with different concentrations of HS. EROD activity was significantly induced (3-6-fold) in the gills of fish exposed to water from all lakes except the lake with the lowest concentration of HS. All tested concentrations of AHA and N.R.-NOM significantly induced gill EROD activity and the induction was dose-dependent. AHA, but neither N.R.-NOM nor lake water, induced EROD activity in the liver. In addition, fish were exposed to the potent CYP1A inducers benzo(a)pyrene (BaP) and PCB126 in combination with AHA. Presence of AHA had no significant effect on EROD induction by BaP or PCB126. The components in HS responsible for EROD induction remain to be identified. Our finding that HS of both natural and synthetic origin induce EROD activity in the gill is of significance for the interpretation of biomonitoring data on EROD activity as well as for the choice of suitable reference waters.
authors.affiliation: Department of Environmental Toxicology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden.
authors.forename: Carin
authors.initials: C
authors.lastname: Andersson
authors.forename: Alexandra
authors.initials: A
authors.lastname: Abrahamson
authors.forename: Björn
authors.initials: B
authors.lastname: Brunström
authors.forename: Jan
authors.initials: J
authors.lastname: Orberg
mesh_terms: D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water / Q000737:chemistry; D005880:Gills / Q000187:drug effects* / Q000378:metabolism; D006812:Humic Substances / Q000032:analysis / Q000633:toxicity*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D023701:Smegmamorpha / Q000378:metabolism*; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical; D019363:Cytochrome P-450 CYP1A1