G-CSF–induced mobilization of HSCs/HPCs in DBA/2 mice. Data are plotted as a percentage of mobilization, where G-CSF is equal to 100% for each progenitor subtype. Treatment with either Diprotin A alone or Val-Pyr per mouse was observed to have little or no effect on the mobilization of progenitors. Diprotin A or Val-Pyr treatment during G-CSF mobilization resulted in a significant reduction in (A) CFU-GMs (P < .01), (B) BFU-Es (P = .02), and (C) CFU-GEMMs (P < .01) compared with G-CSF alone. Error bars represent SEMs.