Figure 5: Effect of bosentan on thrombin-induced lung fibroblasts proliferation. Normal (A) and scleroderma (B) lung fibroblasts were serum-deprived overnight and stimulated with/without thrombin and/or bosentan for 24 hours; Quick Cell Proliferation Assay was performed in accordance with the manufacturer’s instructions (see Materials and Methods). The data are presented as optical density determined at 450 nm. The experiments were performed three times and mean values ± SD are presented. The *asterisk represents statistically significant differences between cells stimulated with thrombin versus cells stimulated with thrombin and bosentan; ** asterisks represent cells stimulated with bosentan versus non-stimulated cells.