A rapid method of preparing complex organohalogen extracts from avian eggs: Applications to in vitro toxicogenomics screening.

Double-crested cormorants (DCCO) are piscivorous birds that breed in variably contaminated colonies across the Laurentian Great Lakes of North America. Collection and preparation of environmentally relevant extracts from eggs that contain variable concentrations of organohalogen contaminants (OHCs) represents a minimally invasive approach to characterize potential effects of exposure using in vitro bioassays. In this study, a rapid, efficient lipid freeze-filtration extraction method was used to prepare extracts from DCCO eggs collected from five breeding colonies that had variable OHC burdens. Extracts, solubilized in DMSO, were administered to chicken embryonic hepatocytes (CEH) to determine effects on cell viability, 7-ethoxyresorufin-O-deethylase (EROD) activity and mRNA expression using a chicken ToxChip PCR array. EROD EC50 values were lower for extracts with greater OHC burdens and thus, permitted an initial ranking of colonies based on the efficacy of eliciting an aryl hydrocarbon receptor-mediated response. The ToxChip PCR array data provided a more exhaustive, pathway-based evaluation of extract effects; variability in the transcriptomic profiles was associated with OHC burdens. For example, extracts from Mud Island (MUD; Detroit River) had among the highest OHC burdens and elicited a greater biochemical (EROD EC50  = 0.005) and transcriptomic response (22/43 genes altered on the array) in CEH compared to the least contaminated site; Mandarte Island - EROD EC50  = 0.172; 8/43 genes altered. Avian eggs represent a useful biomonitoring tool for determining complex mixture effects and the combination of a rapid extraction method, an in vitro bioassay and targeted endpoint evaluation (e.g. biochemical and transcriptomic) show great promise as environmental effects monitoring approaches. This article is protected by copyright. All rights reserved.