Figure 1. NAD+/NADH ratios in long-term cultured C2C12 myoblasts. (A) NAD+, NADH, and total NAD concentrations of C2C12 myoblasts (2×105 cells/well and 4×105 cells/well) cultured for 24 and 72 h, respectively. *, P < 0.05 for comparison of NAD+ concentrations between cells cultured for 24 h and 72 h; #, P < 0.05 for comparison of NADH concentrations between cells cultured for 24 h and 72 h. &, P < 0.05 for comparison of total NAD+ concentrations between cells cultured for 24 h and 72 h. (B) NAD+/NADH ratio of C2C12 myoblasts (2×105 cells/well) cultured for 24 and 72 h; *, P < 0.05 versus cells cultured for 24 h group. (C) NAD+/NADH ratio of C2C12 myoblasts (4×105 cells/well) cultured for 24 and 72 h; *, P < 0.05 versus cells cultured for 24 h group. (D) NAD+/NADH ratio of C2C12 myoblasts (2×105 cells/well), which were cultured for 24 h, and then treated by lactate (10 mM), pH6 medium, and 48 h medium (collected from C2C12 myoblasts which were cultured at 4×105 cells/well for 48 h) for 24 h, respectively. *, P < 0.05 versus control group (Con, receiving no treatment). All data shown as mean ± SEM. Statistical tests were done by the Student's t test.