Figure 2: Effect of bosentan on thrombin-induced α–smooth muscle actin (SMA) expression. Normal (A) and scleroderma (B) lung fibroblasts were serum-deprived overnight, then treated with various concentration of thrombin and/or bosentan for 24 hours. Cell lysate proteins (40μg) were separated by SDSpolyacrylamide gel electrophoresis and immunoblotted with anti-SMA antibody. The immunoblots were then stripped and re-blotted with anti-β-actin antibody from Sigma as a loading control. The images were scanned and analyzed with NIH Imaging software. Densitometric analysis of immunoblots from 3 independent experiments is presented. The *asterisk represents statistically significant differences between cells stimulated with thrombin versus cells stimulated with thrombin and bosentan.