Figure 4: DNA synthesis regulated by thrombin and bosentan in normal (A) and scleroderma (B) lung fibroblasts. Cells were stimulated with/without thrombin and/or bosentan for 30 hours, and [3H] thymidine incorporation was measured as detailed under Materials and Methods. 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.