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

Double‐crested cormorants 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 represents a minimally invasive approach to characterize potential effects of exposure using in vitro bioassays. In the present study, a rapid, efficient lipid freeze‐filtration extraction method was used to prepare extracts from double‐crested cormorant eggs collected from 5 breeding colonies that had variable organohalogen contaminant burdens. Extracts, solubilized in dimethyl sulfoxide, were administered to chicken embryonic hepatocytes (CEHs) to determine effects on cell viability, 7‐ethoxyresorufin‐O‐deethylase (EROD) activity, and messenger RNA expression using a chicken ToxChip polymerase chain reaction (PCR) array. The EROD median effect concentration (EC50) values were lower for extracts with greater organohalogen contaminant 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 organohalogen contaminant burdens. For example, extracts from Mud Island (Detroit River, MI, USA) had among the highest organohalogen contaminant burdens and elicited a greater biochemical (EROD EC50 = 0.005) and transcriptomic response (22/43 genes altered on the array) in CEHs compared with the least contaminated site, which was Mandarte Island (BC, Canada; 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 (biochemical and transcriptomic) shows great promise as an environmental effects monitoring approach. Environ Toxicol Chem 2019;38:811–819. © 2019 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.