Identification of Major Dioxin-Like Compounds and Androgen Receptor Antagonist in Acid-Treated Tissue Extracts of High Trophic-Level Animals

We evaluated the applicability of combining <i>in vitro</i> bioassays with instrument analyses to identify potential endocrine disrupting pollutants in sulfuric acid-treated extracts of liver and/or blubber of high trophic-level animals. Dioxin-like and androgen receptor (AR) antagonistic activities were observed in Baikal seals, common cormorants, raccoon dogs, and finless porpoises by using a panel of rat and human cell-based chemical-activated luciferase gene expression (CALUX) reporter gene bioassays. On the other hand, no activity was detected in estrogen receptor α (ERα)-, glucocorticoid receptor (GR)-, progesterone receptor (PR)-, and peroxisome proliferator-activated receptor γ2 (PPARγ2)-CALUX assays with the sample amount applied. All individual samples (<i>n</i> = 66) showed dioxin-like activity, with values ranging from 21 to 5500 pg CALUX-2,3,7,8-tetrachlorodibenzo-<i>p</i>-dioxin equivalent (TEQ)/g-lipid. Because dioxins are expected to be strong contributors to CALUX-TEQs, the median theoretical contribution of dioxins calculated from the result of chemical analysis to the experimental CALUX-TEQs was estimated to explain up to 130% for all the tested samples (<i>n</i> = 54). Baikal seal extracts (<i>n</i> = 31), but not other extracts, induced AR antagonistic activities that were 8–150 μg CALUX-flutamide equivalent (FluEQ)/g-lipid. <i>p,p′</i>-DDE was identified as an important causative compound for the activity, and its median theoretical contribution to the experimental CALUX-FluEQs was 59% for the tested Baikal seal tissues (<i>n</i> = 25). Our results demonstrate that combining <i>in vitro</i> CALUX assays with instrument analysis is useful for identifying persistent organic pollutant-like compounds in the tissue of wild animals on the basis of <i>in vitro</i> endocrine disruption toxicity.