PT-100 stimulates hematopoiesis in normal mice. (A) Structure of PT-100. (B) Levels of erythroid and myeloid CFUs (×10^–4) in BALB/c mice after oral administration of saline (□) or 5 μg PT-100 (▪) twice daily for 5 days. Erythroid and myeloid CFUs in spleens and BM were assayed as described in “Materials and methods.” CFU-Es were observed after 2 to 3 days in culture, whereas BFU-Es and CFU-GMs were observed after 7 to 9 days. Data are expressed as mean splenic CFCs ± SEM of 3 independent experiments (n = 11-12 mice/treatment group) and mean BM CFCs ± SEM of 2 experiments (n = 7-8 mice/treatment group). (C) Changes in ANCs in mice administered saline (○) or 20 μg PT-100 (•) orally and twice daily. ANCs were determined by standard differential counting. Data are expressed as the mean ± SD of 5 mice/group, using discrete groups at each point in time. Changes in ANCs are representative of 2 independent experiments. (D) Changes in serum G-CSF (○,•) and IL-6 (□,▪) levels in mice administered saline (open symbols) or PT-100 (filled symbols) as described in panel C. Serum cytokine levels were determined by ELISA, and data are expressed as mean ± SD from 5 mice/group. Changes in G-CSF and IL-6 levels are representative of 3 independent experiments.