Free radical production induced by the addition of IS. MC3T3-E1 cells were seeded in 96-well plates, IS was added, and free radical production was measured after the indicated time. (A) Free radical production increased with time in a dose-dependent manner. (B) IS-induced free radical production was suppressed by 0.5 mM N-acetylcysteine (NAC). The data represent the mean from six replicates ns in each group.