Fig. 2. NO reduces MMP-13 protein and MMP-13 activity during MC3T3-E1 differentiation. MC3T3-E1 cells were induced to differentiate with ascorbic acid (AA) and ß-glycerol phosphate (ßGP), and analyzed at the time points indicated in the presence or absence of 200 µM 1400W. (A) Immunoblot of MMP-13 and MT1-MMP (n=3). (B) Gelatin zimography (n=3). (C) Detection of MMP-13 activity by using a fluorogenic substrate from culture supernatants (n=3, mean ± s.d.).