Osteoclast numbers increase in association with elevation of urine DPyr levels after G-CSF administration in mice. Mice were treated with G-CSF (□), pamidronate + G-CSF (▪), pamidronate (•), or saline (○). Six mice of each group were killed on each time point and TRAP⁺ osteoclast numbers (A) and urine DPyr levels (B) were measured as described in Materials and Methods. These data represent the mean ± SEM.