Figure 2.

Panel A, Western blots of muscle lysates show the presence of unprocessed (45–55 kDa) and the processed (32 kDa) myostatin in young and old mice, respectively. Testosterone (T) effectively suppresses the processed myostatin levels in the aged muscles. The gels are representative of two animals at each group from one of three separate experiments. GAPDH in the immunoblot is shown as a loading control. Panel B, Quantification of band intensities shows significant suppression of the processed myostatin levels after treatment with 1 cm testosterone. Values are mean ± sem. Means with letters BC are not different from means with either superscript letter B or C but are significantly (P < 0.05) different from means with letter A. Panel C, EIA assay reveals a significant increase in phospho-JNK levels in old animals when compared with young animals, which can be significantly prevented by testosterone treatment at both doses. Values are mean ± sem. Means with unlike letters are significantly (P < 0.001) different. Panel D, Phopho-p38 MAPK levels were significantly increased in aged muscles compared with that of young animals. However, testosterone treatment had no effect on aging-associated activation of p38 MAPK. Values are mean ± sem. Means with unlike letters are significantly (P < 0.05) different.