Endothelin-1 (ET-1) induced the expression of type I collage through the non-Smad pathway in normal dermal fibroblasts. A, B. Quiescent normal dermal fibroblasts were treated with the indicated concentration of ET-1 for 24 hours. mRNA levels of the human α2 (I) collagen (COL1A2) gene were determined by reverse transcription (RT) real-time PCR ( A ). Under the same condition, whole cell lysates were subjected to immunoblotting with anti-type I collagen antibody ( B ). (C, D) Quiescent normal dermal fibroblasts were treated with 200 nM of ET-1 for the indicated period of time. mRNA levels of the COL1A2 gene (C) and the protein levels of type I collagen in whole cell lysates (D) were evaluated by RT real-time PCR and immunoblotting, respectively. (E) Quiescent normal dermal fibroblasts were treated with SIS3 (3 μM) or methanol. One hour later, some of the cells were treated with 200 nM of ET-1 for 3 or 24 hours. mRNA levels of the COL1A2 gene were assessed by RT real-time PCR. The graph represents fold change in mRNA levels of the COL1A2 gene and protein levels of type I collagen, which were quantified by densitometry, in response to ET-1 in comparison to unstimulated controls, which were arbitrarily set at 1. *P <0.05 versus control cells untreated with ET-1. α1(I), α1(I) procollagen; α2(I), α2(I) procollagen; AU, arbitrary unit.