Fig. 5. MIs reversibly inhibit MyoD expression. Asynchronous myoblasts were incubated in 20% serum alone (1), 2% HS alone (2), 2% HS + vehicle (3), 30 mM BDM (4) or 15 µM ML7 (5) for 24 hours. (A) MyoD (red) was detected in 50% of control cells, but was reduced in both BDM and ML7 treated cells (Scale bar: 10 µm). (B) The frequency of MyoD expression (mean ± s.e.m., n=2). (C) Replacement of MIs with growth medium leads to a rapid return of MyoD expression (mean ± s.e.m., n=2). The differences in the kinetics and plateau of the recovery curves may reflect differences in extent of cell cycle synchrony, the enzymatic properties of the two target enzymes or their effects on upstream regulators of MyoD.