Dose-dependent effects of TCDD in juvenile rainbow trout

We investigated the effects of chronic TCDD exposure on global gene expression in developing rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout (0.18±0.01g) were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100ppb, and ten fish were sampled and pooled from each group for microarray experiments at 28 days after initiation of the exposure. Gene expression analysis was performed using the Genomics Research on All Salmonids Project (cGRASP) 16K cDNA microarrays. TCDD-responsive whole body transcripts identified in the microarray experiments have putative functions involved in various biological processes including cellular process, metabolic process, biological regulation, and response to stimulus. In addition, TCDD caused leisons in multiple organ systems in juvenile rainbow, including skin, oropharynx, liver, gas bladder, intestine, pancreas, nose and kidney. Juvenile rainbow trout (0.18±0.01g) were fed Biodiet starter (Bio-Oregon) (4% body weight per day) with TCDD added at 0, 0.1, 1, 10 and 100 ppb. Fish were sampled after 28 days. Total RNA from individual fish was isolated using TRIzol reagent (Invitrogen). Total RNA of ten control trout were pooled as a common reference which were labeled with Cy3. Total RNA of ten fish of each treatment were labeled wih Cy5. cDNA were synthesized using SuperScript II Reverse Transcriptase (Invitrogen) (1 μg pooled RNA per synthesis). Targets were labeled using the Array 900 Expression Array Detection kit (Genisphere) following the manufacture protocol. 1µg RNA of pooled ten control fish were labled with Cy3 and 1µg RNA of pooled ten TCDD-treated fish were labled with Cy5, then day-swap was performed. Two arrays were run for each comparison. Microarrays were scanned at 10 µm resolution using a ScanArray Express (PerkinElmer Life Sciences, Inc, Boston, MA). The photomultiplier tube settings (PMT) for Cy3 and Cy5 were 70 and 65-66, respectively. TIFF images of arrays were generated with ScanArray Express software (PerkinElmer). Fluorescence intensity data for Cy3 and Cy5 channels were extracted from TIFF images using ImaGene 7.5 software (BioDiscovery Inc., El Segundo, CA). Background correction, data transformation (setting background corrected values < 0.01 to 0.01), Lowess normalization, and analysis (e.g. fold-change calculations) were performed using GeneSpring GX 7.3 (Agilent Technologies, Palo Alto, CA)