PT-100 administration promotes neutrophil regeneration in mouse model of neutropenia. BALB/c mice were injected intraperitoneally with CYP (220 mg/kg) on day 0 and were administered saline or PT-100 orally and twice daily, starting on day 3. (A) Changes in ANCs in mice receiving 0.1 μg(▪), 2 μg(•), or 5 μg (▴) PT-100 or saline (○) for 5 days. (B) Changes in ANCs in mice receiving saline (○) or 2 μg PT-100 administered for 2 (▪), 3 (▴), or 5 (•) days. (C) Changes in serum G-CSF levels in mice receiving 2 μg PT-100 (•) or saline (○). (D) Changes in ANCs on days 5 (□) and 6 (▪) in mice receiving saline, 30 μg or 5 μg PT-100, or NAc-VBP as indicated on the abscissa. ANC and G-CSF levels were determined by standard differential counts and ELISA, respectively, and are expressed as mean ± SD from 4 to 5 mice per group. Data are representative of 6 independent ANC experiments and 3 independent G-CSF experiments. Significant P values are indicated in “Results.” Mean ANC and G-CSF levels in normal mice are indicated by the horizontal lines.