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Figure 5 Identification of angiotensin II (Ang II)-responsive cis-elements in endothelin 1 (ET-1) promoter. (A) A series of deletion mutants containing various lengths of ET-1 promoter region were transfected into cardiac fibroblasts. Transfected cells were stimulated with Ang II (100 nM) for 24 h, and chloramphenicol acetyltransferase (CAT) activities were measured. Stepwise 5'-deletion constructs were depicted (top). Bars represent mean (±SEM, n = 3 per group). CAT activity of each construct in the presence or absence of Ang II were assayed. CAT 2 and CAT 3 were used as positive or negative controls for CAT assay respectively (bottom). (B) Wild type (204 bp) or AP-1 mutant of ET-1 promoter-CAT plasmid was transfected into cardiac fibroblasts. Cells were stimulated with Ang II (100 nM) for 24 h. The mutation of AP-1 strongly abolished the responsiveness to Ang II stimulation. The results are shown as mean ± SEM (n = 3 per group). *p < 0.05 versus control (Student t test); #p < 0.05 versus Ang II alone (analysis of variance).