FIGURE 5.

Delayed activation of p38 MAPK and Akt pathways regulates fibroblast growth. Immunoblot analysis of cell lysate from primary muscle fibroblasts. a, treated with 300 ng/ml of myostatin for increasing duration demonstrating expression levels of phospho-p38 MAPK (P-P38MAPK), total p38 MAPK (P38MAPK), phospho-Akt (P-AKT), total Akt (AKT), and α-tubulin, as a loading control; b, untreated (CON) or treated with 300 ng/ml of myostatin (MSTN), myostatin plus 10 μm SB202190 (M+SB), or SB202190 alone (SB). c and d, fibroblasts treated for 24 h with 300 ng/ml myostatin (MSTN), myostatin and rapamycin (M+R), or rapamycin alone (R). c, evaluated by immunoblot of PCNA, phospho-mTOR (P-mTOR), total mTOR (mTOR), and α-tubulin, as a loading control. d, evaluated by histogram of mean densities of PCNA immunoreactive band relative to control (CON). n = 3 for each data point; **, p < 0.005. e and f, [³H]thymidine incorporation (e) and [³H]proline incorporation (f) of treated fibroblasts. n = 5 for each data point; ***, p < 0.001.