Relative quantity of transcripts of the 25S rRNA (transcribed by RNA polymerase I), act (encoding actin), and gpd (encoding GAPDH) genes (transcribed by RNA polymerase II) under various conditions for determination of the internal standard (Figure 4). Drugs were added into 48 h culture, and total RNA was extracted from each culture at 24 h after the drug addition. Each real-time RT-PCRs was performed using 3 ng total RNA. Error bars show the SD for 4 biological repetitions. A common letter indicates cases where values were insignificantly different between drug groups (P < 0.05), estimated by Turkey's HSD test following one-way factorial ANOVA. Primers 5'-CGTCAACGACCCCTTCATTG-3' and 5'-CGACATAGAGCTTGCCGTCCT-3' were used for the gpd gene. The other primers are listed in Sakamoto et al. (2010).