Identification of the responsive element to endothelin-1 (ET-1) stimulation in the human α2 (I) collagen (COL1A2) promoter. Normal dermal fibroblasts were transfected with 2 μg of the indicated 5′-deletion of the COL1A2/CAT construct and incubated for 48 hours. In some experiments, cells were treated with ET-1 (200 nM) for the last 24 hours. Values represent CAT mRNA levels relative to those of untreated cells transfected with the same COL1A2/CAT construct (100). The mean and SD from five separate experiments are shown. *P <0.05 versus control cells untreated with ET-1.