Comparison of differential expression levels using RNA array and Northern blotting. For RNA array and Northern blot, the normalized intensity of fluorescence or radioactivity signal was used to compare expression levels in controls and drug treated rats (n = 5 per group) for each gene. Expression levels were expressed in folds of control (fold changes) by dividing signal intensity of each drug treated rat by mean signal intensity of control rats. Log fold changes shown (y-axis) represent log2 transformed values for drug treated rats. The p-values are for comparison of expression levels in controls and drug treated rats. Data are presented as mean ± SD. Asterisk (*) indicate significance levels: * = p < 0.05; ** = p < 0.01; *** = p < 0.001.