Fig. 2.

Time course of type IIb myosin heavy chain (MyHC) mRNA levels (A) and type IIb MyHC promoter activity (B) in differentiating C₂C₁₂ myocytes. C₂C₁₂ myocytes were harvested after 1–4 days of differentiation in DM (control) or DM with 250 ng/ml IGF-I (IGF-I). Type IIb MyHC mRNA was not detectable at the time differentiation was initiated (day 0) nor after 1 day of differentiation under control or IGF-I conditions (data not shown). Type IIb MyHC mRNA was detectable after 2 days under IGF-I conditions, but because of the scale of the graph the data are not visible. Data are reported as the average ± SE of n = 4 wells/group. *P < 0.05 from time-matched control, #P < 0.05 from earliest day control, $P < 0.05 from earliest day IGF-I.