Expression data from mouse liver on multisetp-exposure to ethylbenzene

The processes involved in the adaptation of animals to environmental factors such as chemicals have not yet been fully elucidated. We focused on the adaptive potential of the mouse liver against hepatotoxic chemical-induced injury. We used microarrays to determine genes with adaptive transcriptional regulation against ethylbenzene, hepatotoxic chemical, on multistep-exposure. Four animal groups received the following treatments: phosphate-buffered saline (PBS) followed by PBS (P+P), ethylbenzene followed by PBS (E+P), PBS followed by ethylbenzene (P+E), and ethylbenzene followed by ethylbenzene (E+E). For the first exposure, ethylbenzene (7 mmol kg-1) or PBS (equivalent volume to ethylbenzene) was intraperitoneally injected twice at a 24 h interval. After 7 days of normal feeding, each animal group was treated with ethylbenzene (7 mmol kg-1) or PBS as the secondary exposure. The mice were sacrificed 5 h after the secondary exposure for RNA extraction and hybridization on Affymetrix. The number of mice of each group is as follows, P+P, E+P = 3. P+E, E+E = 5. Specimens from mice of each group were pooled, and 10 μg RNA from each pool was used for cRNA synthesis.