which include polychlorinated biphenyls (PCBs), dibenzofuSpecies-Specific Recombinant Cell Lines as Bioassay Systems rans (PCDFs), and dibenzo-p-dioxins (PCDDs) as well as for the Detection of 2,3,7,8-Tetrachlorodibenzo-p-dioxin-like many other subclasses of PCDHs (Giesy et al., 1994a). These known to bioaccumulate and biomagnify in the food chain Exposure to specific polychlorinated diaromatic hydrocarbons (Ballschmitter et al., 1989; Tanabe et al., 1987; Webster and (PCDH), such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, di- Commoner, 1994; Giesy et al., 1994a,b). Exposure to and oxin), produces a wide variety of species-and tissue-specific toxic bioaccumulation of PCDHs has been observed to produce a and biological effects. Many of these responses are mediated by variety of species-and tissue-specific effects, such as tumor of PCDHs involve costly and time-consuming traditional instrumental analysis methods, such as gas chromatography Polychlorinated diaromatic hydrocarbons (PCDHs) 2 are a (GC) separation and mass spectrometry (MS). The identifidiverse group of widespread environmental contaminants, cation and quantification of these compounds is complicated by the fact that techniques and standards for identifying many of the congeners and isomers do not exist. In addition,

Sediments at many locations in Dutch waters are heavily Chemical-Activated Luciferase Expression (CALUX): A Novel polluted with polyhalogenated aromatic hydrocarbons in Vitro Bioassay for Ah Receptor Active Compounds in Sedi-(PHAHs) such as polychlorodibenzo-p-dioxins (PCDDs), ments and Pore Water. MURK, A. J., LEGLER, J., DENISON, M. S., -dibenzofurans (PCDFs), and -biphenyls (PCBs). Of the GIESY, J. P., VAN (TCDD) is the prototypical and most potent member. This study demonstrates that the novel in vitro CALUX (chemi-PHAHs are persistent and lipophilic and elicit a number cal-activated luciferase expression) assay is a rapid, sensitive assay of species-specific, toxic responses in vertebrates, including for assessing the toxic potency of (mixtures of) aryl hydrocarbon hepatoxicity, body weight loss, thymic atrophy, impairment very sensitive to PHAH-induced toxicity, especially whenThe sensitivity and linear working range was slightly better than for the ethoxyresorufin O-deethylase (EROD) assay in H4IIE wild exposed during early life stages, i.e., egg to larval stadium type cells. The primary improvement of the CALUX assay com- (Kleeman et al., 1986). Typical toxic responses are malforpared to the EROD assay, however, is that the CALUX assay is mations, hemorrhages, and pericardial edema (Walker et al., insensitive to substrate inhibition. The CALUX activity induced 1991, 1992). PHAH-contaminated sediments thus may pose by organic extracts from 450-mg aliquots of sediment or 250-ml a serious threat to aquatic species and their predators, includaliquots of pore water corresponded with the instrumentally ana-ing fish-eating birds, mammals, and humans. Therefore a lyzed degree of pollution of the sediment. Using pore water, only rapid, inexpensive assay is needed for monitoring the toxic a simple and rapid extraction procedure was needed, without addipotency of a great number of samples. We feel that our Of the hundreds of existing PHAHs, those with one or no ortho-substituted halogen can assume a planar configuration, making them approximate isostereomeres TCDD. The mechanism of action for these relatively toxic, planar PHAHs has

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