DRB (65 μM), a transcription inhibitor, was added to ZOL-treated and -untreated cell cultures, and RNA was extracted at 0, 8, 16 and 24 h. The steady-state levels of BSP mRNA were analysed using real-time RT–PCR, normalized to 18 S rRNA, expressed as the percentage of the initial 0 h control and plotted as a function of time. The decay of (A) BSP mRNA and (B) GAPDH mRNA in Saos-2 cells. The half-lives of BSP and GAPDH mRNA were calculated by linear extrapolation. Each experiment was performed three times with similar results.