Stimulation of MMP-12 mRNA expression by IL-1β in ASMC. Cells were incubated in the absence or presence of IL-1β at 10 ng/ml for 1–24 hours (A, B), or for 24 hours over 0.01 to 10 ng/ml (C). MMP-12 and GAPDH mRNA expression was analysed by RT-PCR (A) or real-time RT-PCR (B,C). Results (B,C) were expressed as a ratio of target gene to GAPDH mRNA control and are the mean ± SEM from three ASMC donors. **P < 0.01 compared with control.