IGF-1 treatment of C2C12 cells activates MAP kinase and PI 3-kinase signaling pathways. C2C12 cells were serum-starved for 18 hours prior to stimulation with IGF-1 (100 nM) for 0, 1, 2, 4, 8, or 24 hours. Cells were lysed in detergent containing buffer and 20 ug of protein from each time point was separated on a 10% SDS polyacrylamide gel. Western blots were performed using phosphospecific antibodies to Erk (p42/p44) and Akt (p473) as well as antibodies that detect total protein. Actin is shown as a loading control.