FIGURE 7.

Myocardin is required for insulin and IGF-1 to induce hypertrophy. A, myocardin is up-regulated in response to insulin treatment. The neonatal rat cardiomyocytes were treated with 20 μg/ml insulin, and then harvested at the indicated times for the detection of myocardin using immunoblot. A representative result of three independent experiments is shown. B, myocardin is required for insulin to induce hypertrophy. Cardiomyocytes were infected with Ad-myocardin-RNAi or Ad-myocardin-S-RNAi at an m.o.i. of 80. 30 h after infection cells were treated with insulin. Analysis of myocardin levels by immunoblot was performed 1 h after insulin treatment (upper panel). Cell surface area measurement was performed 48 h after insulin treatment (lower panel). *, p < 0.05 versus insulin alone. C, myocardin is required for IGF-1 to induce hypertrophy. Cardiomyocytes were infected with Ad-myocardin-RNAi or Ad-myocardin-S-RNAi as described for B, except that 30 ng/ml IGF-1 was used. Analysis of myocardin levels by immunoblot was performed 1 h after IGF-1 treatment (upper panel). Cell surface area measurement was performed 48 h after IGF-1 treatment (lower panel). *, p < 0.05 versus IGF-1 alone. Data in B and C are expressed as the mean ± S.E. of three independent experiments.