DNA fragmentation in erythroid progenitor cells challenged with LY294002. Day 8 cells that contained 62% ± 13% erythroid progenitor cells were suspended at a concentration of 5 × 10⁵/mL in 0.5 mL serum-free medium supplemented with 2 U/mL EPO in the presence of 50 μmol/L LY294002 (A) or with various concentrations of LY294002 (B). After incubation for the indicated periods (A) or for 24 hours (B), the cells were collected and washed twice with PBS. DNA fragmentation was determined by quantifying the amount of oligonucleosome-bound DNA in the 20,000× gsupernatant of cell lysates. Data represent the mean from 2 determinations.