ABSTRACT: Male Sprague-Dawley rats weighing 250-300 g were purchased from Japan SLC Co. (Shizuoka, Japan). The animals were housed under a daily controlled 12-h light and 12-h dark cycle at 23 °C with free access to rat chow (Japan SLC Co.) and water for 1 week prior to the experiments. Rats were intraperitoneally injected with 75 mg/kg body weight of ANIT (alpha-naphtylisothiocyanate) dissolved in olive oil (7.5 mg/mL). Control animals received an injection of the same volume of olive oil. Groups of three rats were sacrificed under ether anesthesia at 12, 18, 24 hr after ANIT or olive oil administration. At the time of sacrifice, the right lateral liver lobe was removed and flash-frozen in liquid nitrogen and stored at -80 °C. Total RNA isolated from frozen livers using TRIzol reagent (Invitrogen Co., Carlsbad, CA) was mixed to minimize variation among animals. Poly(A) RNA was purified using Oligotex-dT30 (Takara Shuzo Co., Ltd., Kyoto, Japan) in accordance with manufacturer’s instructions. Fluorescence-labeled probes were prepared by reverse transcription using a superscript II reverse transcriptase (Invitrogen Co.) and cyanine-3- and cyanine-5-dUTP (Perkin-Elmer Inc., Wellesley, MA). Poly(A) RNAs derived from rats that has administrated ANIT and from those that has administrated olive oil were labeled with cyanine-5 and cyanine-3, respectively, and vise varsa. Fluorescence-labeled probes were purified using a MinElute PCR Products Purification Kit (Quiagen GmbH, Hilden, Germany) in accordance with manufacturer’s instructions. Each purified probe was suspended in hybridization buffer containing 1.6 mg/mL poly(A) (Roche Diagnostics, Basel, Switzerland) and yeast tRNA (Roche Diagnostics), 0.67 mg/mL herring sperm, 16% 20 x SSC and 0.3% SDS and applied to a cDNA microarray containing 1,800 rat genes on a slide glass (Asahi Technoglass Co., Tokyo, Japan). Three house-keeping genes (GAPDH, HPRT and b-actin) and rat unrelated traits (Lambda DNA) were also spotted on the slide as internal positive and negative controls, respectively. Hybridization was carried out twice to eliminate any dye bias. In one experiment, duplicate slides were hybridized with probes derived from rats which were administrated ANIT and control rats that had been labeld with cyanine-3 and cyanine-5, respectively. In a replicate experiment, other duplicate slides were hybridized with probes derived from ANIT-treated and control rats that had been labeled with cyanine-5 and cyanine-3, respectively (color swap). Then, the slides were cover-slipped and incubated in a sealed chamber (Asahi Technoglass Co.) for 16 hrs under a humidified (65 °C) condition. After being washed in low-stringency buffer (2 x SSC and 0.1% SDS), high-stringency buffer (0.2 x SSC and 0.1% SDS) and 0.2 x SSC and then rinsing with 99.5% ethanol, the slide was dried by centrifugation at low speed and used for scanning. Fluorescence was scanned by using a ScanArray 4000 (Packard BioChip Technologies, Billerica, MA) and quantified by using QuantArray Software (Packard BioChip Technologies, Billerica, MA). Keywords: time-course
