Acceleration of recovery from CY-induced neutropenia by SCH 14988. Mice were dosed as described in Materials and Methods and sacrificed on days 3, 5, 6, 8, or 10. Peripheral blood cells or spleen cells were collected, washed, and enumerated, and Gr-1 and Mac-1 staining were analyzed. Data is expressed as the mean ± standard error of mean (SEM) number of granulocytes (Gr-1⁺Mac-1⁺) per milliliter of blood (A) or per spleen (B). ▵ indicates normal age-matched control mice; • indicates CY-treated, vehicle-treated mice; ▪ indicates CY-treated, SCH 14988-treated mice. Differences between the vehicle-treated and SCH 14988-treated groups from days 5, 6, 8, and 10 are statistically significant at P < .05, as determined by the Students' t-test. Administration of the two likely metabolic products of SCH 14988 (see Results) or of analogs that did not induce G-CSF production in vitro had no effect on neutrophil recovery (data not shown).