Figure 1: Effect of thrombin on ET-1 expression in normal and scleroderma lung fibroblasts. Cells were serum-deprived overnight and treated with various concentration of thrombin for 24 hours. Medium was collected and ET-1 secretion was determined by Human Endothelin-1 Immunoassay. Data are shown are mean ± SD of three experiments each performed in duplicate. The *asterisk represents statistically significant differences between cells stimulated with thrombin and versus nonstimulated cells.