| Abstrakt: |
In vitro induction of ethoxyresorufin O-deethylase (EROD) activity in cell cultures is an extensively validated tool for measuring overall potencies of mixtures of halogenated aromatic hydrocarbons (HAHs) in samples from the abiotic or biotic environment. For risk assessment with special attention to effects in wild birds, an assay was developed that makes use of chicken embryo hepatocytes. However, it was questioned whether compound-specific responses are consistent at the various developmental stages. The results of our present study show that there are considerable differences between early and late embryonal and post-hatching stages. The induction of EROD was measured in primary chicken hepatocyte cultures. The cells were isolated at day 14 and day 19 of embryonal development and at day 1 post hatching. Hepatocytes were exposed in vitro to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126, IUPAC nomenclature) and 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118). The respective compounds were chosen as representives for dioxins, furans, non-ortho PCBs, and mono-ortho PCBs. These groups of chemicals have been identified as environmental contaminants with major dioxin-like effects that are mediated by a common receptor, the arylhydrocarbon (Ah) receptor. At all developmental stages, TCDF was more potent than TCDD. Relative potencies (RP = EC50 tcdd/EC50 hah) decreased in the order TCDF50) and the maximum EROD activity ( Y max) of all compounds were lower in hepatocyte cultures from 14-day-old embryos than those from 19-day-old embryos or 1-day-old hatchlings. RPs were comparable in 19-day-old embryos and in hatchlings, but significantly different in 14-day-old embryos. [ABSTRACT FROM AUTHOR] |
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