Fig. 3. Phosphorylation of myosin light chain (MLC) after mechanical loading. (A) Immunoblots of phosphorylated MLC were prepared from Rat-2 cells treated with force. The ratio of phosphorylated to total MLC was computed from densitometry measurements of immunoblots. Data are given mean ± s.d. compared with the no-force ratio (designated as 1). (B) Positive control for phosphorylation of MLC. Cells were treated with ionomycin (2 µM) for 0, 15, 30 or 60 minutes (0', 15', 30' or 60', respectively). Cell lysates were immunoblotted for phosphorylated MLC (P-MLC).